diff --git a/TODO b/TODO
new file mode 100644
index 0000000000..aab3581489
--- /dev/null
+++ b/TODO
@@ -0,0 +1,23 @@
+- check 
+    new fvMesh
+    new fvMeshSubset
+for consistency with createMesh.H
+
+
+
+- Check the following:
+
+doc/changes/inotify.txt
+ 
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/applications/solvers/DNS/dnsFoam/readTransportProperties.H b/applications/solvers/DNS/dnsFoam/readTransportProperties.H
index 77af096bf8..0d80908542 100644
--- a/applications/solvers/DNS/dnsFoam/readTransportProperties.H
+++ b/applications/solvers/DNS/dnsFoam/readTransportProperties.H
@@ -7,7 +7,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/DNS/dnsFoam/readTurbulenceProperties.H b/applications/solvers/DNS/dnsFoam/readTurbulenceProperties.H
index 20fd654cef..ba1d5dcd80 100644
--- a/applications/solvers/DNS/dnsFoam/readTurbulenceProperties.H
+++ b/applications/solvers/DNS/dnsFoam/readTurbulenceProperties.H
@@ -7,7 +7,7 @@
             "turbulenceProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/basic/laplacianFoam/createFields.H b/applications/solvers/basic/laplacianFoam/createFields.H
index 3359f2896c..616afe1a88 100644
--- a/applications/solvers/basic/laplacianFoam/createFields.H
+++ b/applications/solvers/basic/laplacianFoam/createFields.H
@@ -23,7 +23,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/basic/scalarTransportFoam/createFields.H b/applications/solvers/basic/scalarTransportFoam/createFields.H
index 54a0bc45ec..07731be3d6 100644
--- a/applications/solvers/basic/scalarTransportFoam/createFields.H
+++ b/applications/solvers/basic/scalarTransportFoam/createFields.H
@@ -39,7 +39,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/combustion/PDRFoam/XiModels/XiEqModels/SCOPEXiEq/SCOPEXiEq.C b/applications/solvers/combustion/PDRFoam/XiModels/XiEqModels/SCOPEXiEq/SCOPEXiEq.C
index 385b9e53f0..32b525859e 100644
--- a/applications/solvers/combustion/PDRFoam/XiModels/XiEqModels/SCOPEXiEq/SCOPEXiEq.C
+++ b/applications/solvers/combustion/PDRFoam/XiModels/XiEqModels/SCOPEXiEq/SCOPEXiEq.C
@@ -62,7 +62,7 @@ Foam::XiEqModels::SCOPEXiEq::SCOPEXiEq
                 "combustionProperties",
                 Su.mesh().time().constant(),
                 Su.mesh(),
-                IOobject::MUST_READ
+                IOobject::MUST_READ_IF_MODIFIED
             )
         ),
         thermo
diff --git a/applications/solvers/combustion/PDRFoam/createFields.H b/applications/solvers/combustion/PDRFoam/createFields.H
index 74a18ab6f5..233383ab1c 100644
--- a/applications/solvers/combustion/PDRFoam/createFields.H
+++ b/applications/solvers/combustion/PDRFoam/createFields.H
@@ -110,7 +110,7 @@
             "PDRProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/combustion/PDRFoam/readCombustionProperties.H b/applications/solvers/combustion/PDRFoam/readCombustionProperties.H
index 9f4435b251..acc5cb7868 100644
--- a/applications/solvers/combustion/PDRFoam/readCombustionProperties.H
+++ b/applications/solvers/combustion/PDRFoam/readCombustionProperties.H
@@ -7,7 +7,7 @@
             "combustionProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/combustion/XiFoam/readCombustionProperties.H b/applications/solvers/combustion/XiFoam/readCombustionProperties.H
index da0a3a94a2..58b0626fb4 100644
--- a/applications/solvers/combustion/XiFoam/readCombustionProperties.H
+++ b/applications/solvers/combustion/XiFoam/readCombustionProperties.H
@@ -7,7 +7,7 @@
             "combustionProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/combustion/dieselEngineFoam/readCombustionProperties.H b/applications/solvers/combustion/dieselEngineFoam/readCombustionProperties.H
index 687d83ea94..84cf9b9756 100644
--- a/applications/solvers/combustion/dieselEngineFoam/readCombustionProperties.H
+++ b/applications/solvers/combustion/dieselEngineFoam/readCombustionProperties.H
@@ -7,7 +7,7 @@ IOdictionary combustionProperties
         "combustionProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     )
 );
diff --git a/applications/solvers/combustion/fireFoam/createFields.H b/applications/solvers/combustion/fireFoam/createFields.H
index 95bda05606..9a6274bb1a 100644
--- a/applications/solvers/combustion/fireFoam/createFields.H
+++ b/applications/solvers/combustion/fireFoam/createFields.H
@@ -65,7 +65,7 @@ IOdictionary combustionProperties
         "combustionProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     )
 );
diff --git a/applications/solvers/combustion/reactingFoam/readChemistryProperties.H b/applications/solvers/combustion/reactingFoam/readChemistryProperties.H
index ab51afe283..f0bcf7597f 100644
--- a/applications/solvers/combustion/reactingFoam/readChemistryProperties.H
+++ b/applications/solvers/combustion/reactingFoam/readChemistryProperties.H
@@ -7,7 +7,7 @@ IOdictionary chemistryProperties
         "chemistryProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE,
         false
     )
diff --git a/applications/solvers/combustion/rhoReactingFoam/readChemistryProperties.H b/applications/solvers/combustion/rhoReactingFoam/readChemistryProperties.H
index ab51afe283..f0bcf7597f 100644
--- a/applications/solvers/combustion/rhoReactingFoam/readChemistryProperties.H
+++ b/applications/solvers/combustion/rhoReactingFoam/readChemistryProperties.H
@@ -7,7 +7,7 @@ IOdictionary chemistryProperties
         "chemistryProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE,
         false
     )
diff --git a/applications/solvers/compressible/rhoCentralFoam/readThermophysicalProperties.H b/applications/solvers/compressible/rhoCentralFoam/readThermophysicalProperties.H
index 435bcb7745..5a63169d12 100644
--- a/applications/solvers/compressible/rhoCentralFoam/readThermophysicalProperties.H
+++ b/applications/solvers/compressible/rhoCentralFoam/readThermophysicalProperties.H
@@ -9,7 +9,7 @@ IOdictionary thermophysicalProperties
         "thermophysicalProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     )
 );
diff --git a/applications/solvers/compressible/rhoSonicFoam/readThermodynamicProperties.H b/applications/solvers/compressible/rhoSonicFoam/readThermodynamicProperties.H
index 1fc57fc5fd..4e19adaae4 100644
--- a/applications/solvers/compressible/rhoSonicFoam/readThermodynamicProperties.H
+++ b/applications/solvers/compressible/rhoSonicFoam/readThermodynamicProperties.H
@@ -7,7 +7,7 @@
             "thermodynamicProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/compressible/rhopSonicFoam/readThermodynamicProperties.H b/applications/solvers/compressible/rhopSonicFoam/readThermodynamicProperties.H
index 3b8c82c8e5..2be7ce63ff 100644
--- a/applications/solvers/compressible/rhopSonicFoam/readThermodynamicProperties.H
+++ b/applications/solvers/compressible/rhopSonicFoam/readThermodynamicProperties.H
@@ -7,7 +7,7 @@
             "thermodynamicProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/compressible/sonicDyMFoam/readThermodynamicProperties.H b/applications/solvers/compressible/sonicDyMFoam/readThermodynamicProperties.H
index 1fc57fc5fd..4e19adaae4 100644
--- a/applications/solvers/compressible/sonicDyMFoam/readThermodynamicProperties.H
+++ b/applications/solvers/compressible/sonicDyMFoam/readThermodynamicProperties.H
@@ -7,7 +7,7 @@
             "thermodynamicProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/compressible/sonicDyMFoam/readTransportProperties.H b/applications/solvers/compressible/sonicDyMFoam/readTransportProperties.H
index 1502e2033a..c30f65b445 100644
--- a/applications/solvers/compressible/sonicDyMFoam/readTransportProperties.H
+++ b/applications/solvers/compressible/sonicDyMFoam/readTransportProperties.H
@@ -7,7 +7,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/compressible/sonicLiquidFoam/readThermodynamicProperties.H b/applications/solvers/compressible/sonicLiquidFoam/readThermodynamicProperties.H
index d8dad7d800..82f3655f46 100644
--- a/applications/solvers/compressible/sonicLiquidFoam/readThermodynamicProperties.H
+++ b/applications/solvers/compressible/sonicLiquidFoam/readThermodynamicProperties.H
@@ -7,7 +7,7 @@
             "thermodynamicProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/compressible/sonicLiquidFoam/readTransportProperties.H b/applications/solvers/compressible/sonicLiquidFoam/readTransportProperties.H
index 1502e2033a..c30f65b445 100644
--- a/applications/solvers/compressible/sonicLiquidFoam/readTransportProperties.H
+++ b/applications/solvers/compressible/sonicLiquidFoam/readTransportProperties.H
@@ -7,7 +7,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/discreteMethods/molecularDynamics/mdEquilibrationFoam/readmdEquilibrationDict.H b/applications/solvers/discreteMethods/molecularDynamics/mdEquilibrationFoam/readmdEquilibrationDict.H
index b94745d9df..3f43981907 100644
--- a/applications/solvers/discreteMethods/molecularDynamics/mdEquilibrationFoam/readmdEquilibrationDict.H
+++ b/applications/solvers/discreteMethods/molecularDynamics/mdEquilibrationFoam/readmdEquilibrationDict.H
@@ -7,7 +7,7 @@ IOdictionary mdEquilibrationDict
         "mdEquilibrationDict",
         runTime.system(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     )
 );
diff --git a/applications/solvers/electromagnetics/electrostaticFoam/createFields.H b/applications/solvers/electromagnetics/electrostaticFoam/createFields.H
index 64522273b8..04c86c4edb 100644
--- a/applications/solvers/electromagnetics/electrostaticFoam/createFields.H
+++ b/applications/solvers/electromagnetics/electrostaticFoam/createFields.H
@@ -7,7 +7,7 @@
             "physicalProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/electromagnetics/magneticFoam/createFields.H b/applications/solvers/electromagnetics/magneticFoam/createFields.H
index a3712c19aa..22d4008921 100644
--- a/applications/solvers/electromagnetics/magneticFoam/createFields.H
+++ b/applications/solvers/electromagnetics/magneticFoam/createFields.H
@@ -21,7 +21,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/electromagnetics/mhdFoam/createFields.H b/applications/solvers/electromagnetics/mhdFoam/createFields.H
index 04e05c032d..fb5a004932 100644
--- a/applications/solvers/electromagnetics/mhdFoam/createFields.H
+++ b/applications/solvers/electromagnetics/mhdFoam/createFields.H
@@ -7,7 +7,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/financial/financialFoam/createFields.H b/applications/solvers/financial/financialFoam/createFields.H
index 6cdbbe2bde..dc0da4d2a3 100644
--- a/applications/solvers/financial/financialFoam/createFields.H
+++ b/applications/solvers/financial/financialFoam/createFields.H
@@ -7,7 +7,7 @@
             "financialProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/heatTransfer/chtMultiRegionFoam/regionProperties/regionProperties.C b/applications/solvers/heatTransfer/chtMultiRegionFoam/regionProperties/regionProperties.C
index 89eaaabd48..f85e8f5440 100644
--- a/applications/solvers/heatTransfer/chtMultiRegionFoam/regionProperties/regionProperties.C
+++ b/applications/solvers/heatTransfer/chtMultiRegionFoam/regionProperties/regionProperties.C
@@ -36,7 +36,7 @@ Foam::regionProperties::regionProperties(const Time& runTime)
             "regionProperties",
             runTime.time().constant(),
             runTime.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/applications/solvers/incompressible/boundaryFoam/createFields.H b/applications/solvers/incompressible/boundaryFoam/createFields.H
index e99a990013..90a6664989 100644
--- a/applications/solvers/incompressible/boundaryFoam/createFields.H
+++ b/applications/solvers/incompressible/boundaryFoam/createFields.H
@@ -44,7 +44,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/incompressible/channelFoam/readTransportProperties.H b/applications/solvers/incompressible/channelFoam/readTransportProperties.H
index 87c93c9195..abaee647c7 100644
--- a/applications/solvers/incompressible/channelFoam/readTransportProperties.H
+++ b/applications/solvers/incompressible/channelFoam/readTransportProperties.H
@@ -6,7 +6,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/applications/solvers/incompressible/icoFoam/createFields.H b/applications/solvers/incompressible/icoFoam/createFields.H
index 6a7d6b9a80..02093c3938 100644
--- a/applications/solvers/incompressible/icoFoam/createFields.H
+++ b/applications/solvers/incompressible/icoFoam/createFields.H
@@ -7,7 +7,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/incompressible/shallowWaterFoam/readGravitationalAcceleration.H b/applications/solvers/incompressible/shallowWaterFoam/readGravitationalAcceleration.H
index d609c18614..d8a8bf8d06 100644
--- a/applications/solvers/incompressible/shallowWaterFoam/readGravitationalAcceleration.H
+++ b/applications/solvers/incompressible/shallowWaterFoam/readGravitationalAcceleration.H
@@ -7,7 +7,7 @@ IOdictionary gravitationalProperties
         "gravitationalProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     )
 );
diff --git a/applications/solvers/lagrangian/coalChemistryFoam/readChemistryProperties.H b/applications/solvers/lagrangian/coalChemistryFoam/readChemistryProperties.H
index ab51afe283..f0bcf7597f 100644
--- a/applications/solvers/lagrangian/coalChemistryFoam/readChemistryProperties.H
+++ b/applications/solvers/lagrangian/coalChemistryFoam/readChemistryProperties.H
@@ -7,7 +7,7 @@ IOdictionary chemistryProperties
         "chemistryProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE,
         false
     )
diff --git a/applications/solvers/lagrangian/incompressibleUncoupledKinematicParcelFoam/createFields.H b/applications/solvers/lagrangian/incompressibleUncoupledKinematicParcelFoam/createFields.H
index 179ac149ba..0ad057e229 100644
--- a/applications/solvers/lagrangian/incompressibleUncoupledKinematicParcelFoam/createFields.H
+++ b/applications/solvers/lagrangian/incompressibleUncoupledKinematicParcelFoam/createFields.H
@@ -7,7 +7,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/lagrangian/porousExplicitSourceReactingParcelFoam/readChemistryProperties.H b/applications/solvers/lagrangian/porousExplicitSourceReactingParcelFoam/readChemistryProperties.H
index ab51afe283..f0bcf7597f 100644
--- a/applications/solvers/lagrangian/porousExplicitSourceReactingParcelFoam/readChemistryProperties.H
+++ b/applications/solvers/lagrangian/porousExplicitSourceReactingParcelFoam/readChemistryProperties.H
@@ -7,7 +7,7 @@ IOdictionary chemistryProperties
         "chemistryProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE,
         false
     )
diff --git a/applications/solvers/lagrangian/reactingParcelFilmFoam/createFields.H b/applications/solvers/lagrangian/reactingParcelFilmFoam/createFields.H
index 8048acd648..909d0351f7 100644
--- a/applications/solvers/lagrangian/reactingParcelFilmFoam/createFields.H
+++ b/applications/solvers/lagrangian/reactingParcelFilmFoam/createFields.H
@@ -97,7 +97,7 @@
             "additionalControls",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/lagrangian/reactingParcelFilmFoam/readChemistryProperties.H b/applications/solvers/lagrangian/reactingParcelFilmFoam/readChemistryProperties.H
index ab51afe283..f0bcf7597f 100644
--- a/applications/solvers/lagrangian/reactingParcelFilmFoam/readChemistryProperties.H
+++ b/applications/solvers/lagrangian/reactingParcelFilmFoam/readChemistryProperties.H
@@ -7,7 +7,7 @@ IOdictionary chemistryProperties
         "chemistryProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE,
         false
     )
diff --git a/applications/solvers/lagrangian/reactingParcelFoam/readChemistryProperties.H b/applications/solvers/lagrangian/reactingParcelFoam/readChemistryProperties.H
index ab51afe283..f0bcf7597f 100644
--- a/applications/solvers/lagrangian/reactingParcelFoam/readChemistryProperties.H
+++ b/applications/solvers/lagrangian/reactingParcelFoam/readChemistryProperties.H
@@ -7,7 +7,7 @@ IOdictionary chemistryProperties
         "chemistryProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE,
         false
     )
diff --git a/applications/solvers/multiphase/bubbleFoam/createFields.H b/applications/solvers/multiphase/bubbleFoam/createFields.H
index 9367838a52..57bb7e88d5 100644
--- a/applications/solvers/multiphase/bubbleFoam/createFields.H
+++ b/applications/solvers/multiphase/bubbleFoam/createFields.H
@@ -91,7 +91,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/multiphase/bubbleFoam/createRASTurbulence.H b/applications/solvers/multiphase/bubbleFoam/createRASTurbulence.H
index 1ae6219fd6..015cfbb837 100644
--- a/applications/solvers/multiphase/bubbleFoam/createRASTurbulence.H
+++ b/applications/solvers/multiphase/bubbleFoam/createRASTurbulence.H
@@ -5,7 +5,7 @@
             "RASProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/multiphase/cavitatingFoam/readThermodynamicProperties.H b/applications/solvers/multiphase/cavitatingFoam/readThermodynamicProperties.H
index d3fbb9307a..3740f10563 100644
--- a/applications/solvers/multiphase/cavitatingFoam/readThermodynamicProperties.H
+++ b/applications/solvers/multiphase/cavitatingFoam/readThermodynamicProperties.H
@@ -7,7 +7,7 @@
             "thermodynamicProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/multiphase/interPhaseChangeFoam/phaseChangeTwoPhaseMixtures/phaseChangeTwoPhaseMixture/phaseChangeTwoPhaseMixtureNew.C b/applications/solvers/multiphase/interPhaseChangeFoam/phaseChangeTwoPhaseMixtures/phaseChangeTwoPhaseMixture/phaseChangeTwoPhaseMixtureNew.C
index bffffd6aae..27da4ad0c0 100644
--- a/applications/solvers/multiphase/interPhaseChangeFoam/phaseChangeTwoPhaseMixtures/phaseChangeTwoPhaseMixture/phaseChangeTwoPhaseMixtureNew.C
+++ b/applications/solvers/multiphase/interPhaseChangeFoam/phaseChangeTwoPhaseMixtures/phaseChangeTwoPhaseMixture/phaseChangeTwoPhaseMixtureNew.C
@@ -46,7 +46,7 @@ Foam::phaseChangeTwoPhaseMixture::New
                 "transportProperties",
                 U.time().constant(),
                 U.db(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/applications/solvers/multiphase/settlingFoam/createFields.H b/applications/solvers/multiphase/settlingFoam/createFields.H
index c8e05c4209..75d19c6779 100644
--- a/applications/solvers/multiphase/settlingFoam/createFields.H
+++ b/applications/solvers/multiphase/settlingFoam/createFields.H
@@ -50,7 +50,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
@@ -184,7 +184,7 @@
             "RASProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/multiphase/twoPhaseEulerFoam/createFields.H b/applications/solvers/multiphase/twoPhaseEulerFoam/createFields.H
index 8a12690581..308a1089fb 100644
--- a/applications/solvers/multiphase/twoPhaseEulerFoam/createFields.H
+++ b/applications/solvers/multiphase/twoPhaseEulerFoam/createFields.H
@@ -7,7 +7,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
@@ -153,7 +153,7 @@
             "interfacialProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/multiphase/twoPhaseEulerFoam/kineticTheoryModels/kineticTheoryModel/kineticTheoryModel.C b/applications/solvers/multiphase/twoPhaseEulerFoam/kineticTheoryModels/kineticTheoryModel/kineticTheoryModel.C
index 611ce8fa16..57096ebd0c 100644
--- a/applications/solvers/multiphase/twoPhaseEulerFoam/kineticTheoryModels/kineticTheoryModel/kineticTheoryModel.C
+++ b/applications/solvers/multiphase/twoPhaseEulerFoam/kineticTheoryModels/kineticTheoryModel/kineticTheoryModel.C
@@ -56,7 +56,7 @@ Foam::kineticTheoryModel::kineticTheoryModel
             "kineticTheoryProperties",
             Ua_.time().constant(),
             Ua_.mesh(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/applications/solvers/multiphase/twoPhaseEulerFoam/readPPProperties.H b/applications/solvers/multiphase/twoPhaseEulerFoam/readPPProperties.H
index 3acbf758d0..c1b319cbc9 100644
--- a/applications/solvers/multiphase/twoPhaseEulerFoam/readPPProperties.H
+++ b/applications/solvers/multiphase/twoPhaseEulerFoam/readPPProperties.H
@@ -5,7 +5,7 @@
             "ppProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/stressAnalysis/solidDisplacementFoam/readMechanicalProperties.H b/applications/solvers/stressAnalysis/solidDisplacementFoam/readMechanicalProperties.H
index 91bd5f3da2..9f256bd689 100644
--- a/applications/solvers/stressAnalysis/solidDisplacementFoam/readMechanicalProperties.H
+++ b/applications/solvers/stressAnalysis/solidDisplacementFoam/readMechanicalProperties.H
@@ -7,7 +7,7 @@
             "mechanicalProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/solvers/stressAnalysis/solidDisplacementFoam/readThermalProperties.H b/applications/solvers/stressAnalysis/solidDisplacementFoam/readThermalProperties.H
index a4c3082fb5..12e10a607b 100644
--- a/applications/solvers/stressAnalysis/solidDisplacementFoam/readThermalProperties.H
+++ b/applications/solvers/stressAnalysis/solidDisplacementFoam/readThermalProperties.H
@@ -7,7 +7,7 @@
             "thermalProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/test/LduMatrix/createFields.H b/applications/test/LduMatrix/createFields.H
index ea64f13026..57714aa787 100644
--- a/applications/test/LduMatrix/createFields.H
+++ b/applications/test/LduMatrix/createFields.H
@@ -7,7 +7,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/test/dataEntry/testDataEntry.C b/applications/test/dataEntry/testDataEntry.C
index 583701322b..456f0d478d 100644
--- a/applications/test/dataEntry/testDataEntry.C
+++ b/applications/test/dataEntry/testDataEntry.C
@@ -48,7 +48,7 @@ int main(int argc, char *argv[])
             "dataEntryProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/test/fvSolutionCombine/fvSolutionCombine.C b/applications/test/fvSolutionCombine/fvSolutionCombine.C
index a98d803bf3..19abc81611 100644
--- a/applications/test/fvSolutionCombine/fvSolutionCombine.C
+++ b/applications/test/fvSolutionCombine/fvSolutionCombine.C
@@ -116,7 +116,7 @@ int main(int argc, char *argv[])
             dictName,
             "system",
             runTime,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/applications/utilities/errorEstimation/estimateScalarError/estimateScalarError.C b/applications/utilities/errorEstimation/estimateScalarError/estimateScalarError.C
index 9b305731db..8b2339233c 100644
--- a/applications/utilities/errorEstimation/estimateScalarError/estimateScalarError.C
+++ b/applications/utilities/errorEstimation/estimateScalarError/estimateScalarError.C
@@ -57,7 +57,7 @@ int main(int argc, char *argv[])
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/errorEstimation/icoErrorEstimate/icoErrorEstimate.C b/applications/utilities/errorEstimation/icoErrorEstimate/icoErrorEstimate.C
index 33486ec301..05a7e5c57c 100644
--- a/applications/utilities/errorEstimation/icoErrorEstimate/icoErrorEstimate.C
+++ b/applications/utilities/errorEstimation/icoErrorEstimate/icoErrorEstimate.C
@@ -56,7 +56,7 @@ int main(int argc, char *argv[])
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/errorEstimation/icoMomentError/icoMomentError.C b/applications/utilities/errorEstimation/icoMomentError/icoMomentError.C
index 57629b5980..d0f668c8c9 100644
--- a/applications/utilities/errorEstimation/icoMomentError/icoMomentError.C
+++ b/applications/utilities/errorEstimation/icoMomentError/icoMomentError.C
@@ -57,7 +57,7 @@ int main(int argc, char *argv[])
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/errorEstimation/momentScalarError/momentScalarError.C b/applications/utilities/errorEstimation/momentScalarError/momentScalarError.C
index 72744a9f8d..246380a029 100644
--- a/applications/utilities/errorEstimation/momentScalarError/momentScalarError.C
+++ b/applications/utilities/errorEstimation/momentScalarError/momentScalarError.C
@@ -58,7 +58,7 @@ int main(int argc, char *argv[])
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/mesh/advanced/autoRefineMesh/autoRefineMesh.C b/applications/utilities/mesh/advanced/autoRefineMesh/autoRefineMesh.C
index c2f3640f2d..3ef371188e 100644
--- a/applications/utilities/mesh/advanced/autoRefineMesh/autoRefineMesh.C
+++ b/applications/utilities/mesh/advanced/autoRefineMesh/autoRefineMesh.C
@@ -639,7 +639,7 @@ int main(int argc, char *argv[])
         "motionProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     );
 
@@ -669,7 +669,7 @@ int main(int argc, char *argv[])
             "autoRefineMeshDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/mesh/advanced/combinePatchFaces/combinePatchFaces.C b/applications/utilities/mesh/advanced/combinePatchFaces/combinePatchFaces.C
index 0b09b7859d..21c9f5867a 100644
--- a/applications/utilities/mesh/advanced/combinePatchFaces/combinePatchFaces.C
+++ b/applications/utilities/mesh/advanced/combinePatchFaces/combinePatchFaces.C
@@ -74,7 +74,7 @@ void checkSnapMesh
             "snapMeshDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/mesh/advanced/modifyMesh/modifyMesh.C b/applications/utilities/mesh/advanced/modifyMesh/modifyMesh.C
index 7cd57e792d..befadc88e2 100644
--- a/applications/utilities/mesh/advanced/modifyMesh/modifyMesh.C
+++ b/applications/utilities/mesh/advanced/modifyMesh/modifyMesh.C
@@ -346,7 +346,7 @@ int main(int argc, char *argv[])
             "modifyMeshDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/mesh/advanced/selectCells/edgeStats.C b/applications/utilities/mesh/advanced/selectCells/edgeStats.C
index 561cef9bfd..103d963be5 100644
--- a/applications/utilities/mesh/advanced/selectCells/edgeStats.C
+++ b/applications/utilities/mesh/advanced/selectCells/edgeStats.C
@@ -78,7 +78,7 @@ Foam::edgeStats::edgeStats(const polyMesh& mesh)
         "motionProperties",
         mesh.time().constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     );
 
diff --git a/applications/utilities/mesh/advanced/selectCells/selectCells.C b/applications/utilities/mesh/advanced/selectCells/selectCells.C
index 8f79846050..f5ad8412f7 100644
--- a/applications/utilities/mesh/advanced/selectCells/selectCells.C
+++ b/applications/utilities/mesh/advanced/selectCells/selectCells.C
@@ -346,7 +346,7 @@ int main(int argc, char *argv[])
             "selectCellsDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/mesh/conversion/foamToStarMesh/getTimeIndex.H b/applications/utilities/mesh/conversion/foamToStarMesh/getTimeIndex.H
index 85a92405dd..d722c432e3 100644
--- a/applications/utilities/mesh/conversion/foamToStarMesh/getTimeIndex.H
+++ b/applications/utilities/mesh/conversion/foamToStarMesh/getTimeIndex.H
@@ -29,7 +29,7 @@
                     runTime.timeName(),
                     "uniform",
                     runTime,
-                    IOobject::MUST_READ,
+                    IOobject::MUST_READ_IF_MODIFIED,
                     IOobject::NO_WRITE,
                     false
                 )
diff --git a/applications/utilities/mesh/conversion/foamToSurface/getTimeIndex.H b/applications/utilities/mesh/conversion/foamToSurface/getTimeIndex.H
index 85a92405dd..d722c432e3 100644
--- a/applications/utilities/mesh/conversion/foamToSurface/getTimeIndex.H
+++ b/applications/utilities/mesh/conversion/foamToSurface/getTimeIndex.H
@@ -29,7 +29,7 @@
                     runTime.timeName(),
                     "uniform",
                     runTime,
-                    IOobject::MUST_READ,
+                    IOobject::MUST_READ_IF_MODIFIED,
                     IOobject::NO_WRITE,
                     false
                 )
diff --git a/applications/utilities/mesh/generation/blockMesh/blockMeshApp.C b/applications/utilities/mesh/generation/blockMesh/blockMeshApp.C
index 3f8086bb80..a0baebaae7 100644
--- a/applications/utilities/mesh/generation/blockMesh/blockMeshApp.C
+++ b/applications/utilities/mesh/generation/blockMesh/blockMeshApp.C
@@ -121,7 +121,7 @@ int main(int argc, char *argv[])
                   : dictPath
                 ),
                 runTime,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
@@ -137,7 +137,7 @@ int main(int argc, char *argv[])
                 runTime.constant(),
                 polyMeshDir,
                 runTime,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/applications/utilities/mesh/generation/extrudeMesh/extrudeMesh.C b/applications/utilities/mesh/generation/extrudeMesh/extrudeMesh.C
index 1d0ce53e73..9d28de4109 100644
--- a/applications/utilities/mesh/generation/extrudeMesh/extrudeMesh.C
+++ b/applications/utilities/mesh/generation/extrudeMesh/extrudeMesh.C
@@ -218,7 +218,7 @@ int main(int argc, char *argv[])
             runTimeExtruded.constant(),
             regionDir,
             runTimeExtruded,
-            IOobject::MUST_READ
+            IOobject::MUST_READ_IF_MODIFIED
         )
     );
 
diff --git a/applications/utilities/mesh/generation/snappyHexMesh/snappyHexMesh.C b/applications/utilities/mesh/generation/snappyHexMesh/snappyHexMesh.C
index e93112a431..7ced14726d 100644
--- a/applications/utilities/mesh/generation/snappyHexMesh/snappyHexMesh.C
+++ b/applications/utilities/mesh/generation/snappyHexMesh/snappyHexMesh.C
@@ -144,7 +144,7 @@ int main(int argc, char *argv[])
             "decomposeParDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
@@ -157,7 +157,7 @@ int main(int argc, char *argv[])
             "snappyHexMeshDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
        )
     );
diff --git a/applications/utilities/mesh/manipulation/createPatch/createPatch.C b/applications/utilities/mesh/manipulation/createPatch/createPatch.C
index 43652bbbea..7f80d01e5d 100644
--- a/applications/utilities/mesh/manipulation/createPatch/createPatch.C
+++ b/applications/utilities/mesh/manipulation/createPatch/createPatch.C
@@ -532,7 +532,7 @@ int main(int argc, char *argv[])
               : word::null
             ),
             runTime,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/applications/utilities/mesh/manipulation/mirrorMesh/mirrorFvMesh.C b/applications/utilities/mesh/manipulation/mirrorMesh/mirrorFvMesh.C
index f5b79e7de1..96a092fb22 100644
--- a/applications/utilities/mesh/manipulation/mirrorMesh/mirrorFvMesh.C
+++ b/applications/utilities/mesh/manipulation/mirrorMesh/mirrorFvMesh.C
@@ -39,7 +39,7 @@ Foam::mirrorFvMesh::mirrorFvMesh(const IOobject& io)
             "mirrorMeshDict",
             time().system(),
             *this,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/applications/utilities/mesh/manipulation/mirrorMesh/readMirrorDict.H b/applications/utilities/mesh/manipulation/mirrorMesh/readMirrorDict.H
index 6116514701..138898842b 100644
--- a/applications/utilities/mesh/manipulation/mirrorMesh/readMirrorDict.H
+++ b/applications/utilities/mesh/manipulation/mirrorMesh/readMirrorDict.H
@@ -7,7 +7,7 @@
             "mirrorMeshDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/mesh/manipulation/refineMesh/refineMesh.C b/applications/utilities/mesh/manipulation/refineMesh/refineMesh.C
index ba3170d281..f890c84546 100644
--- a/applications/utilities/mesh/manipulation/refineMesh/refineMesh.C
+++ b/applications/utilities/mesh/manipulation/refineMesh/refineMesh.C
@@ -334,7 +334,7 @@ int main(int argc, char *argv[])
                 "refineMeshDict",
                 runTime.system(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
         );
diff --git a/applications/utilities/mesh/manipulation/renumberMesh/renumberMesh.C b/applications/utilities/mesh/manipulation/renumberMesh/renumberMesh.C
index 495e07f290..19a80bac5f 100644
--- a/applications/utilities/mesh/manipulation/renumberMesh/renumberMesh.C
+++ b/applications/utilities/mesh/manipulation/renumberMesh/renumberMesh.C
@@ -483,7 +483,7 @@ int main(int argc, char *argv[])
                 "decomposeParDict",
                 runTime.system(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
         );
diff --git a/applications/utilities/mesh/manipulation/stitchMesh/stitchMesh.C b/applications/utilities/mesh/manipulation/stitchMesh/stitchMesh.C
index 733cef024b..9790aec1e1 100644
--- a/applications/utilities/mesh/manipulation/stitchMesh/stitchMesh.C
+++ b/applications/utilities/mesh/manipulation/stitchMesh/stitchMesh.C
@@ -298,7 +298,7 @@ int main(int argc, char *argv[])
                 args.options()["toleranceDict"],
                 runTime.constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
         );
diff --git a/applications/utilities/mesh/manipulation/topoSet/topoSet.C b/applications/utilities/mesh/manipulation/topoSet/topoSet.C
index 6f1c9957e4..54fd6e0dee 100644
--- a/applications/utilities/mesh/manipulation/topoSet/topoSet.C
+++ b/applications/utilities/mesh/manipulation/topoSet/topoSet.C
@@ -83,7 +83,7 @@ int main(int argc, char *argv[])
             (
                 dictPath,
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
           : IOobject
@@ -91,7 +91,7 @@ int main(int argc, char *argv[])
                 dictName,
                 runTime.system(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
         ) 
diff --git a/applications/utilities/parallelProcessing/decomposePar/decomposePar.C b/applications/utilities/parallelProcessing/decomposePar/decomposePar.C
index a3f6786861..2009375040 100644
--- a/applications/utilities/parallelProcessing/decomposePar/decomposePar.C
+++ b/applications/utilities/parallelProcessing/decomposePar/decomposePar.C
@@ -169,7 +169,7 @@ int main(int argc, char *argv[])
                 runTime.time().system(),
                 regionDir,          // use region if non-standard
                 runTime,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/applications/utilities/parallelProcessing/decomposePar/domainDecomposition.C b/applications/utilities/parallelProcessing/decomposePar/domainDecomposition.C
index 6575c31dd3..2cc5c26b1a 100644
--- a/applications/utilities/parallelProcessing/decomposePar/domainDecomposition.C
+++ b/applications/utilities/parallelProcessing/decomposePar/domainDecomposition.C
@@ -94,7 +94,7 @@ Foam::domainDecomposition::domainDecomposition(const IOobject& io)
             "decomposeParDict",
             time().system(),
             *this,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/applications/utilities/parallelProcessing/redistributeMeshPar/redistributeMeshPar.C b/applications/utilities/parallelProcessing/redistributeMeshPar/redistributeMeshPar.C
index c3a2003d40..5df7310f8e 100644
--- a/applications/utilities/parallelProcessing/redistributeMeshPar/redistributeMeshPar.C
+++ b/applications/utilities/parallelProcessing/redistributeMeshPar/redistributeMeshPar.C
@@ -581,7 +581,7 @@ int main(int argc, char *argv[])
             "decomposeParDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/postProcessing/dataConversion/foamDataToFluent/foamDataToFluent.C b/applications/utilities/postProcessing/dataConversion/foamDataToFluent/foamDataToFluent.C
index d469054ca3..35f6544f4d 100644
--- a/applications/utilities/postProcessing/dataConversion/foamDataToFluent/foamDataToFluent.C
+++ b/applications/utilities/postProcessing/dataConversion/foamDataToFluent/foamDataToFluent.C
@@ -94,7 +94,7 @@ int main(int argc, char *argv[])
                 "foamDataToFluentDict",
                 runTime.system(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
         );
diff --git a/applications/utilities/postProcessing/dataConversion/foamToEnsightParts/getTimeIndex.H b/applications/utilities/postProcessing/dataConversion/foamToEnsightParts/getTimeIndex.H
index ecf12f8b13..491ada9a43 100644
--- a/applications/utilities/postProcessing/dataConversion/foamToEnsightParts/getTimeIndex.H
+++ b/applications/utilities/postProcessing/dataConversion/foamToEnsightParts/getTimeIndex.H
@@ -26,7 +26,7 @@
 
         if (io.headerOk())
         {
-            io.readOpt() = IOobject::MUST_READ;
+            io.readOpt() = IOobject::MUST_READ_IF_MODIFIED;
             IOdictionary timeObject(io);
 
             timeObject.lookup("index") >> timeIndex;
diff --git a/applications/utilities/postProcessing/dataConversion/foamToGMV/readConversionProperties.H b/applications/utilities/postProcessing/dataConversion/foamToGMV/readConversionProperties.H
index b19e03ab19..60b547dfd2 100644
--- a/applications/utilities/postProcessing/dataConversion/foamToGMV/readConversionProperties.H
+++ b/applications/utilities/postProcessing/dataConversion/foamToGMV/readConversionProperties.H
@@ -5,7 +5,7 @@ IOdictionary conversionProperties
         "conversionProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     )
 );
diff --git a/applications/utilities/postProcessing/graphics/PV3Readers/PV3blockMeshReader/vtkPV3blockMesh/vtkPV3blockMesh.C b/applications/utilities/postProcessing/graphics/PV3Readers/PV3blockMeshReader/vtkPV3blockMesh/vtkPV3blockMesh.C
index a7483a210c..d11d2ae5ba 100644
--- a/applications/utilities/postProcessing/graphics/PV3Readers/PV3blockMeshReader/vtkPV3blockMesh/vtkPV3blockMesh.C
+++ b/applications/utilities/postProcessing/graphics/PV3Readers/PV3blockMeshReader/vtkPV3blockMesh/vtkPV3blockMesh.C
@@ -315,7 +315,7 @@ void Foam::vtkPV3blockMesh::updateFoamMesh()
                 dbPtr_().constant(),
                 polyMesh::meshSubDir,
                 dbPtr_(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/applications/utilities/postProcessing/lagrangian/particleTracks/createFields.H b/applications/utilities/postProcessing/lagrangian/particleTracks/createFields.H
index 61c126e492..d7ede226bf 100644
--- a/applications/utilities/postProcessing/lagrangian/particleTracks/createFields.H
+++ b/applications/utilities/postProcessing/lagrangian/particleTracks/createFields.H
@@ -5,7 +5,7 @@ IOdictionary propsDict
         "particleTrackProperties",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ
+        IOobject::MUST_READ_IF_MODIFIED
     )
 );
 
diff --git a/applications/utilities/postProcessing/miscellaneous/execFlowFunctionObjects/execFlowFunctionObjects.C b/applications/utilities/postProcessing/miscellaneous/execFlowFunctionObjects/execFlowFunctionObjects.C
index 8985861582..ccc1ec2948 100644
--- a/applications/utilities/postProcessing/miscellaneous/execFlowFunctionObjects/execFlowFunctionObjects.C
+++ b/applications/utilities/postProcessing/miscellaneous/execFlowFunctionObjects/execFlowFunctionObjects.C
@@ -62,7 +62,7 @@ namespace Foam
                     args["dict"],
                     runTime.system(),
                     runTime,
-                    IOobject::MUST_READ
+                    IOobject::MUST_READ_IF_MODIFIED
                 )
             );
 
@@ -130,7 +130,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
             "RASProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         );
@@ -140,7 +140,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
             "LESProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         );
@@ -184,7 +184,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
                     "transportProperties",
                     runTime.constant(),
                     mesh,
-                    IOobject::MUST_READ,
+                    IOobject::MUST_READ_IF_MODIFIED,
                     IOobject::NO_WRITE
                 )
             );
@@ -214,7 +214,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
             "RASProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         );
@@ -224,7 +224,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
             "LESProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         );
@@ -266,7 +266,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
                     "transportProperties",
                     runTime.constant(),
                     mesh,
-                    IOobject::MUST_READ,
+                    IOobject::MUST_READ_IF_MODIFIED,
                     IOobject::NO_WRITE
                 )
             );
diff --git a/applications/utilities/postProcessing/miscellaneous/pdfPlot/createFields.H b/applications/utilities/postProcessing/miscellaneous/pdfPlot/createFields.H
index ddb1f663ad..d750108654 100644
--- a/applications/utilities/postProcessing/miscellaneous/pdfPlot/createFields.H
+++ b/applications/utilities/postProcessing/miscellaneous/pdfPlot/createFields.H
@@ -5,7 +5,7 @@
             "pdfDict",
             runTime.constant(),
             runTime,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/postProcessing/miscellaneous/postChannel/postChannel.C b/applications/utilities/postProcessing/miscellaneous/postChannel/postChannel.C
index 8c9cb58717..7d71845adb 100644
--- a/applications/utilities/postProcessing/miscellaneous/postChannel/postChannel.C
+++ b/applications/utilities/postProcessing/miscellaneous/postChannel/postChannel.C
@@ -69,7 +69,7 @@ int main(int argc, char *argv[])
             "postChannelDict",
             mesh.time().constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/postProcessing/miscellaneous/postChannel/readTransportProperties.H b/applications/utilities/postProcessing/miscellaneous/postChannel/readTransportProperties.H
index 1e4bdd4292..cef26f6c35 100644
--- a/applications/utilities/postProcessing/miscellaneous/postChannel/readTransportProperties.H
+++ b/applications/utilities/postProcessing/miscellaneous/postChannel/readTransportProperties.H
@@ -7,7 +7,7 @@
             "transportProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/postProcessing/velocityField/Mach/Mach.C b/applications/utilities/postProcessing/velocityField/Mach/Mach.C
index 53bd1a2488..391eee5237 100644
--- a/applications/utilities/postProcessing/velocityField/Mach/Mach.C
+++ b/applications/utilities/postProcessing/velocityField/Mach/Mach.C
@@ -98,7 +98,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
                     "thermodynamicProperties",
                     runTime.constant(),
                     mesh,
-                    IOobject::MUST_READ,
+                    IOobject::MUST_READ_IF_MODIFIED,
                     IOobject::NO_WRITE
                 )
             );
diff --git a/applications/utilities/postProcessing/velocityField/Mach/readThermodynamicProperties.H b/applications/utilities/postProcessing/velocityField/Mach/readThermodynamicProperties.H
index 1fc57fc5fd..4e19adaae4 100644
--- a/applications/utilities/postProcessing/velocityField/Mach/readThermodynamicProperties.H
+++ b/applications/utilities/postProcessing/velocityField/Mach/readThermodynamicProperties.H
@@ -7,7 +7,7 @@
             "thermodynamicProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/postProcessing/velocityField/Pe/Pe.C b/applications/utilities/postProcessing/velocityField/Pe/Pe.C
index a94f474d11..8e26d3f33a 100644
--- a/applications/utilities/postProcessing/velocityField/Pe/Pe.C
+++ b/applications/utilities/postProcessing/velocityField/Pe/Pe.C
@@ -81,7 +81,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
             "RASProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         );
 
@@ -90,7 +90,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
             "LESProperties",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         );
 
@@ -174,7 +174,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
                         "transportProperties",
                         runTime.constant(),
                         mesh,
-                        IOobject::MUST_READ,
+                        IOobject::MUST_READ_IF_MODIFIED,
                         IOobject::NO_WRITE
                     )
                 );
@@ -299,7 +299,7 @@ void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
                         "transportProperties",
                         runTime.constant(),
                         mesh,
-                        IOobject::MUST_READ,
+                        IOobject::MUST_READ_IF_MODIFIED,
                         IOobject::NO_WRITE
                     )
                 );
diff --git a/applications/utilities/preProcessing/boxTurb/readBoxTurbDict.H b/applications/utilities/preProcessing/boxTurb/readBoxTurbDict.H
index 60063b9d22..bcf5625a07 100644
--- a/applications/utilities/preProcessing/boxTurb/readBoxTurbDict.H
+++ b/applications/utilities/preProcessing/boxTurb/readBoxTurbDict.H
@@ -7,7 +7,7 @@
             "boxTurbDict",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/preProcessing/changeDictionary/changeDictionary.C b/applications/utilities/preProcessing/changeDictionary/changeDictionary.C
index 69a201e558..e917feaa70 100644
--- a/applications/utilities/preProcessing/changeDictionary/changeDictionary.C
+++ b/applications/utilities/preProcessing/changeDictionary/changeDictionary.C
@@ -292,7 +292,7 @@ int main(int argc, char *argv[])
             "changeDictionaryDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
@@ -405,7 +405,7 @@ int main(int argc, char *argv[])
                     fieldName,
                     instance,
                     mesh,
-                    IOobject::MUST_READ,
+                    IOobject::MUST_READ_IF_MODIFIED,
                     IOobject::NO_WRITE,
                     false
                 )
diff --git a/applications/utilities/preProcessing/dsmcInitialise/dsmcInitialise.C b/applications/utilities/preProcessing/dsmcInitialise/dsmcInitialise.C
index d779a6427d..edd7d7e752 100644
--- a/applications/utilities/preProcessing/dsmcInitialise/dsmcInitialise.C
+++ b/applications/utilities/preProcessing/dsmcInitialise/dsmcInitialise.C
@@ -50,7 +50,7 @@ int main(int argc, char *argv[])
             "dsmcInitialiseDict",
             mesh.time().system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/preProcessing/engineSwirl/createFields.H b/applications/utilities/preProcessing/engineSwirl/createFields.H
index 596273a9bd..11975d3717 100644
--- a/applications/utilities/preProcessing/engineSwirl/createFields.H
+++ b/applications/utilities/preProcessing/engineSwirl/createFields.H
@@ -7,7 +7,7 @@ IOdictionary engineGeometry
         "engineGeometry",
         runTime.constant(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     )
 );
diff --git a/applications/utilities/preProcessing/foamUpgradeCyclics/foamUpgradeCyclics.C b/applications/utilities/preProcessing/foamUpgradeCyclics/foamUpgradeCyclics.C
index f499ab5030..e615ebe210 100644
--- a/applications/utilities/preProcessing/foamUpgradeCyclics/foamUpgradeCyclics.C
+++ b/applications/utilities/preProcessing/foamUpgradeCyclics/foamUpgradeCyclics.C
@@ -278,7 +278,7 @@ void rewriteField
             fieldName,
             runTime.timeName(),
             runTime,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/applications/utilities/preProcessing/foamUpgradeFvSolution/foamUpgradeFvSolution.C b/applications/utilities/preProcessing/foamUpgradeFvSolution/foamUpgradeFvSolution.C
index 0cdf0cbe77..202ebad86d 100644
--- a/applications/utilities/preProcessing/foamUpgradeFvSolution/foamUpgradeFvSolution.C
+++ b/applications/utilities/preProcessing/foamUpgradeFvSolution/foamUpgradeFvSolution.C
@@ -70,7 +70,7 @@ int main(int argc, char *argv[])
             "fvSolution",
             runTime.system(),
             runTime,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/applications/utilities/preProcessing/mapFields/mapFields.C b/applications/utilities/preProcessing/mapFields/mapFields.C
index 72dae9f838..0eabfe6d3c 100644
--- a/applications/utilities/preProcessing/mapFields/mapFields.C
+++ b/applications/utilities/preProcessing/mapFields/mapFields.C
@@ -291,7 +291,7 @@ int main(int argc, char *argv[])
                 "mapFieldsDict",
                 runTimeTarget.system(),
                 runTimeTarget,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
@@ -310,7 +310,7 @@ int main(int argc, char *argv[])
                 "decomposeParDict",
                 runTimeSource.system(),
                 runTimeSource,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
         );
@@ -375,7 +375,7 @@ int main(int argc, char *argv[])
                 "decomposeParDict",
                 runTimeTarget.system(),
                 runTimeTarget,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
         );
@@ -446,7 +446,7 @@ int main(int argc, char *argv[])
                 "decomposeParDict",
                 runTimeSource.system(),
                 runTimeSource,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
         );
@@ -464,7 +464,7 @@ int main(int argc, char *argv[])
                 "decomposeParDict",
                 runTimeTarget.system(),
                 runTimeTarget,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE
             )
         );
diff --git a/applications/utilities/preProcessing/mdInitialise/mdInitialise.C b/applications/utilities/preProcessing/mdInitialise/mdInitialise.C
index 6e329a271f..abefc1a0b2 100644
--- a/applications/utilities/preProcessing/mdInitialise/mdInitialise.C
+++ b/applications/utilities/preProcessing/mdInitialise/mdInitialise.C
@@ -44,7 +44,7 @@ int main(int argc, char *argv[])
             "mdInitialiseDict",
             runTime.system(),
             runTime,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/applications/utilities/preProcessing/setFields/setFields.C b/applications/utilities/preProcessing/setFields/setFields.C
index b3cbd8c8bc..6676403d53 100644
--- a/applications/utilities/preProcessing/setFields/setFields.C
+++ b/applications/utilities/preProcessing/setFields/setFields.C
@@ -186,7 +186,7 @@ int main(int argc, char *argv[])
             "setFieldsDict",
             runTime.system(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/preProcessing/wallFunctionTable/wallFunctionTableApp.C b/applications/utilities/preProcessing/wallFunctionTable/wallFunctionTableApp.C
index 9c5b70c968..8f9e755d45 100644
--- a/applications/utilities/preProcessing/wallFunctionTable/wallFunctionTableApp.C
+++ b/applications/utilities/preProcessing/wallFunctionTable/wallFunctionTableApp.C
@@ -47,7 +47,7 @@ int main(int argc, char *argv[])
             "wallFunctionDict",
             runTime.constant(),
             mesh,
-            IOobject::MUST_READ
+            IOobject::MUST_READ_IF_MODIFIED
         )
     );
 
diff --git a/applications/utilities/surface/surfaceMeshExport/surfaceMeshExport.C b/applications/utilities/surface/surfaceMeshExport/surfaceMeshExport.C
index dda71c3565..3995031b53 100644
--- a/applications/utilities/surface/surfaceMeshExport/surfaceMeshExport.C
+++ b/applications/utilities/surface/surfaceMeshExport/surfaceMeshExport.C
@@ -241,7 +241,7 @@ int main(int argc, char *argv[])
             importName,
             runTime.constant(),
             runTime,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/applications/utilities/thermophysical/equilibriumCO/equilibriumCO.C b/applications/utilities/thermophysical/equilibriumCO/equilibriumCO.C
index c9c02d199b..7a0c9baae3 100644
--- a/applications/utilities/thermophysical/equilibriumCO/equilibriumCO.C
+++ b/applications/utilities/thermophysical/equilibriumCO/equilibriumCO.C
@@ -62,7 +62,7 @@ int main(int argc, char *argv[])
             "BurcatCpData",
             runTime.constant(),
             runTime,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/doc/changes/inotify.txt b/doc/changes/inotify.txt
new file mode 100644
index 0000000000..146dc55a05
--- /dev/null
+++ b/doc/changes/inotify.txt
@@ -0,0 +1,53 @@
+2010-05-28
+Cleanup of automatic regIOobject rereading.
+
+- all files (usually only IOdictionary) that need to be monitored
+should be registered using MUST_READ_IF_MODIFIED. The MUST_READ should
+be used for objects that do not need to be re-read (e.g. fields).
+In the old system it would actually monitor e.g. 0/U and constant/polyMesh
+files.
+I've temporarily added a warning in IOdictionary if constructed with MUST_READ.
+Same for IOList,IOField,IOMap if constructed with MUST_READ_IF_MODIFIED
+(or is rereading supported?). Please let me know if something does not work or
+you see the warning
+   "Dictionary constructed with IOobject::MUST_READ instead of IOobject::MUST_READ_IF_MODIFIED." << nl
+
+
+- any monitored and modified file will get reloaded from the exact path
+that was monitored. In the old system it would/could do a re-search through all
+times.
+
+
+- all reductions to synchronise status on different processors are done with
+a single reduction instead of one reduction per registered object. This could
+be quite a gain on large numbers of processors.
+
+
+- all file monitoring is done by an instance of 'fileMonitor' in the Time
+class. The fileMonitor class can be found in OSspecific. Default is
+to use the (linux-specific) 'inotify' system calls.
+If compiled with -DFOAM_USE_STAT it will revert to the current 'stat' system
+calls.
+
+
+- inotify does not need timestamps. There is no need for fileModificationSkew
+to allow for time differences. (there can still temporarily be a difference
+in modified status between different processors due to nfs lagging)
+
+
+- fileMonitor stores two hashtables per file so there is a small overhead
+adding and removing files from monitoring.
+
+
+- if runTimeModifiable is false at start of run no files will get monitored,
+however if runTimeModified gets set to false during the run the files
+will still get monitored (though never reloaded). This is only a hypothetical
+problem in that the kernel still stores events for the monitored files. However
+inotify is very efficient - e.g. it gets used to track changes on file systems
+for desktop search engines.
+
+
+- in the old system one could call modified() on any object and get
+and uptodate state. In the new system it will return the state from
+the last runTime++ (which if it triggered any re-reads will have reset the
+state anyway).
diff --git a/src/OSspecific/POSIX/Make/files b/src/OSspecific/POSIX/Make/files
index f6e7c2d55e..788a08105a 100644
--- a/src/OSspecific/POSIX/Make/files
+++ b/src/OSspecific/POSIX/Make/files
@@ -9,6 +9,12 @@ POSIX.C
 cpuTime/cpuTime.C
 clockTime/clockTime.C
 
+/*
+ * Note: fileMonitor assumes inotify by default. Compile with -DFOAM_USE_STAT
+ * to use stat (=timestamps) instead of inotify
+ */
+fileMonitor.C
+
 #ifdef SunOS64
 dummyPrintStack.C
 #else
diff --git a/src/OSspecific/POSIX/Make/options b/src/OSspecific/POSIX/Make/options
index e69de29bb2..b7e9d7211b 100644
--- a/src/OSspecific/POSIX/Make/options
+++ b/src/OSspecific/POSIX/Make/options
@@ -0,0 +1,3 @@
+#ifdef SunOS64
+EXE_INC = -DFOAM_USE_STAT
+#endif
diff --git a/src/OSspecific/POSIX/fileMonitor.C b/src/OSspecific/POSIX/fileMonitor.C
new file mode 100644
index 0000000000..f7f0246c98
--- /dev/null
+++ b/src/OSspecific/POSIX/fileMonitor.C
@@ -0,0 +1,397 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2010-2010 OpenCFD Ltd.
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Class
+    fileMonitor
+
+\*----------------------------------------------------------------------------*/
+
+#include "fileMonitor.H"
+#include "IOstreams.H"
+#include "Pstream.H"
+#include "PackedList.H"
+#include "PstreamReduceOps.H"
+
+#ifdef FOAM_USE_STAT
+#   include "OSspecific.H"
+#   include "regIOobject.H"     // for fileModificationSkew symbol
+#else
+#   include <sys/inotify.h>
+#   include <stropts.h>
+#   include <sys/ioctl.h>
+#endif
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+defineTypeNameAndDebug(Foam::fileMonitor, 0);
+
+template<>
+const char* Foam::NamedEnum<Foam::fileMonitor::fileState, 3>::names[] =
+{
+    "unmodified",
+    "deleted",
+    "modified"
+};
+const Foam::NamedEnum<Foam::fileMonitor::fileState, 3>
+    Foam::fileMonitor::fileStateNames_;
+
+
+namespace Foam
+{
+    // Reduction operator for PackedList of fileState
+    class reduceFileStates
+    {
+        public:
+        unsigned int operator()(const unsigned int x, const unsigned int y)
+        const
+        {
+            // x,y are sets of 2bits representing fileState
+
+            unsigned int mask = 3u;
+            unsigned int shift = 0;
+            unsigned int result = 0;
+
+            while (mask)
+            {
+                // Combine state
+                unsigned int xState = (x & mask) >> shift;
+                unsigned int yState = (y & mask) >> shift;
+
+                // Combine and add to result. Combine is such that UNMODIFIED
+                // wins.
+                unsigned int state = min(xState, yState);
+                result |= (state << shift);
+
+                shift += 2;
+                mask <<= 2;
+            }
+            return result;
+        }
+    };
+
+    // Combine operator for PackedList of fileState
+    class combineReduceFileStates
+    {
+        public:
+        void operator()(unsigned int& x, const unsigned int y) const
+        {
+            x = reduceFileStates()(x, y);
+        }
+    };
+}
+
+
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+#ifdef FOAM_USE_STAT
+void Foam::fileMonitor::checkFiles() const
+{
+    for
+    (
+        HashTable<label, time_t>::iterator iter = lastModified_.begin();
+        iter != lastModified_.end();
+        ++iter
+    )
+    {
+        label watchFd = iter.key();
+        const fileName& fName = watchFile_[watchFd];
+        time_t newTime = lastModified(fName);
+
+        if (newTime == 0)
+        {
+            state_.set(watchFd, DELETED);
+        }
+        else
+        {
+            time_t oldTime = iter();
+            if (newTime > (oldTime + regIOobject::fileModificationSkew))
+            {
+                iter() = newTime;
+                state_.set(watchFd, MODIFIED);
+            }
+            else
+            {
+                state_.set(watchFd, UNMODIFIED);
+            }
+        }
+    }
+}
+#else
+void Foam::fileMonitor::checkFiles() const
+{
+    while (true)
+    {
+        struct timeval zeroTimeout = {0, 0};
+
+        int ready = select
+        (
+            inotifyFd_+1,       // num filedescriptors in watchSet_
+            &watchSet_,         // watchSet_ with only inotifyFd
+            NULL,
+            NULL,
+            &zeroTimeout
+        );
+
+        if (ready < 0)
+        {
+            FatalErrorIn("fileMonitor::updateStates()")
+                << "Problem in issuing select."
+                << abort(FatalError);
+        }
+        else if (FD_ISSET(inotifyFd_, &watchSet_))
+        {
+            struct inotify_event inotifyEvent;
+
+            // Read first event
+            ssize_t nBytes = read
+            (
+                inotifyFd_,
+                &inotifyEvent,
+                sizeof(inotifyEvent)
+            );
+
+            if (nBytes != sizeof(inotifyEvent))
+            {
+                FatalErrorIn("fileMonitor::updateStates(const fileName&)")
+                    << "Read " << label(nBytes) << " ; expected "
+                    << label(sizeof(inotifyEvent))
+                    << abort(FatalError);
+            }
+
+            //Pout<< "mask:" << inotifyEvent.mask << endl;
+            //Pout<< "watchFd:" << inotifyEvent.wd << endl;
+            //Pout<< "watchName:" << watchFile_[inotifyEvent.wd] << endl;
+
+            switch (inotifyEvent.mask)
+            {
+                case IN_DELETE_SELF:
+                {
+                    Map<fileState>::iterator iter =
+                        state_.find(label(inotifyEvent.wd));
+                    iter() = DELETED;
+                }
+                break;
+
+                case IN_MODIFY:
+                case IN_CLOSE_WRITE:
+                {
+                    Map<fileState>::iterator iter =
+                        state_.find(label(inotifyEvent.wd));
+                    iter() = MODIFIED;
+                }
+                break;
+            }
+        }
+        else
+        {
+            // No data. Reset watchSet_
+            FD_SET(inotifyFd_, &watchSet_);
+            return;
+        }
+    }
+}
+#endif
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+// Null constructor
+#ifdef FOAM_USE_STAT
+
+Foam::fileMonitor::fileMonitor()
+:
+    state_(20),
+    watchFile_(20),
+    lastModified_(20)
+{}
+
+#else
+
+Foam::fileMonitor::fileMonitor()
+:
+    state_(20),
+    watchFile_(20),
+    inotifyFd_(inotify_init())
+{
+    //- Add notify descriptor to select set
+    FD_ZERO(&watchSet_);
+    FD_SET(inotifyFd_, &watchSet_);
+}
+
+#endif
+
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+Foam::fileMonitor::~fileMonitor()
+{
+    // Remove any remaining files
+    List<label> watchFds(state_.toc());
+    forAll(watchFds, i)
+    {
+        removeWatch(watchFds[i]);
+    }
+}
+
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+Foam::label Foam::fileMonitor::addWatch(const fileName& fName)
+{
+#ifdef FOAM_USE_STAT
+    label watchFd = lastModified_.size();
+    lastModified_.insert(watchFd, lastModified(fName));
+#else
+    label watchFd = inotify_add_watch
+    (
+        inotifyFd_,
+        fName.c_str(),
+        //IN_ALL_EVENTS
+        IN_CLOSE_WRITE | IN_DELETE_SELF | IN_MODIFY
+    );
+#endif
+
+    if (debug)
+    {
+        Pout<< "fileMonitor : added watch " << watchFd << " on file "
+            << fName << endl;
+    }
+
+    if (watchFd < 0)
+    {
+        WarningIn("fileMonitor::addWatch(const fileName&)")
+            << "could not add watch for file " << fName << endl;
+    }
+    else
+    {
+        state_.insert(watchFd, UNMODIFIED);
+        watchFile_.insert(watchFd, fName);
+    }
+    return watchFd;
+}
+
+
+bool Foam::fileMonitor::removeWatch(const label watchFd)
+{
+    if (debug)
+    {
+        Pout<< "fileMonitor : removing watch " << watchFd << " on file "
+            << watchFile_[watchFd] << endl;
+    }
+
+    state_.erase(watchFd);
+    watchFile_.erase(watchFd);
+#ifdef FOAM_USE_STAT
+    return lastModified_.erase(watchFd);
+#else
+    return inotify_rm_watch(inotifyFd_, int(watchFd)) == 0;
+#endif
+}
+
+
+const Foam::fileName& Foam::fileMonitor::getFile(const label watchFd) const
+{
+    return watchFile_[watchFd];
+}
+
+
+Foam::fileMonitor::fileState Foam::fileMonitor::getState(const label watchFd)
+const
+{
+    return state_[watchFd];
+}
+
+
+void Foam::fileMonitor::updateStates(const bool syncPar) const
+{
+    checkFiles();
+
+    if (syncPar)
+    {
+        PackedList<2> stats(state_.size());
+        label i = 0;
+        forAllConstIter(Map<fileState>, state_, iter)
+        {
+            stats[i++] = (unsigned int)(iter());
+        }
+        // Save local state for warning message below
+        PackedList<2> thisProcStats(stats);
+
+        if (stats.storage().size() == 1)
+        {
+            // Optimisation valid for most cases.
+            reduce(stats.storage()[0], reduceFileStates());
+        }
+        else
+        {
+            Pstream::listCombineGather
+            (
+                stats.storage(),
+                combineReduceFileStates()
+            );
+        }
+
+        i = 0;
+        forAllIter(Map<fileState>, state_, iter)
+        {
+            if (thisProcStats[i] != UNMODIFIED)
+            {
+                if (stats[i] == UNMODIFIED)
+                {
+                    WarningIn("fileMonitor::updateStates(const bool) const")
+                        << "Delaying reading " << watchFile_[iter.key()]
+                        << " due to inconsistent "
+                           "file time-stamps between processors"
+                        << endl;
+                }
+                else
+                {
+                    unsigned int stat = stats[i];
+                    iter() = fileState(stat);
+                }
+            }
+            i++;
+        }
+    }
+}
+
+
+void Foam::fileMonitor::setUnmodified(const label watchFd)
+{
+#ifdef FOAM_USE_STAT
+    lastModified_[watchFd] = lastModified(watchFile_[watchFd]);
+#endif
+
+    Map<fileState>::iterator iter = state_.find(watchFd);
+
+    if (iter == state_.end())
+    {
+        FatalErrorIn("fileMonitor::setUnmodified(const label)")
+            << "Illegal watchFd " << watchFd
+            << abort(FatalError);
+    }
+
+    iter() = UNMODIFIED;
+}
+
+
+// ************************************************************************* //
diff --git a/src/OSspecific/POSIX/fileMonitor.H b/src/OSspecific/POSIX/fileMonitor.H
new file mode 100644
index 0000000000..b9922eb3e2
--- /dev/null
+++ b/src/OSspecific/POSIX/fileMonitor.H
@@ -0,0 +1,159 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2010-2010 OpenCFD Ltd.
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Class
+    fileMonitor
+
+Description
+    Checking for changes to files.
+
+!!!!!!!NOTE:
+    Default is to use inotify (Linux specific, since 2.6.13)
+
+    Compile with FOAM_USE_STAT to use the stat function call.
+
+
+    - works fine except for if file gets deleted and recreated
+    it stops monitoring the file!
+    (does work though if the file gets moved)
+
+SourceFiles
+    fileMonitor.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef fileMonitor_H
+#define fileMonitor_H
+
+#include <sys/types.h>
+#include "Map.H"
+#include "NamedEnum.H"
+#include "labelList.H"
+#include "className.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+
+class fileMonitor;
+
+/*---------------------------------------------------------------------------*\
+                           Class fileMonitor Declaration
+\*---------------------------------------------------------------------------*/
+
+class fileMonitor
+{
+
+public:
+
+    // Public data types
+
+        //- Enumeration defining the file state.
+        enum fileState
+        {
+            UNMODIFIED = 0,
+            DELETED = 1,
+            MODIFIED = 2
+        };
+
+        static const NamedEnum<fileState, 3> fileStateNames_;
+
+private:
+    // Private data
+
+        //- State for all watchFds
+        mutable Map<fileState> state_;
+        
+        //- From watch descriptor to filename
+        HashTable<fileName, label> watchFile_;
+
+#ifdef FOAM_USE_STAT
+
+        //- From watch descriptor to modified time
+        mutable HashTable<label, time_t> lastModified_;
+#else
+        //- File descriptor for the inotify instance
+        int inotifyFd_;
+
+        //- Pre-allocated structure containing file descriptors
+        mutable fd_set watchSet_;
+
+#endif
+        //- Update state_ from any events.
+        void checkFiles() const;
+
+        //- Disallow default bitwise copy construct
+        fileMonitor(const fileMonitor&);
+
+        //- Disallow default bitwise assignment
+        void operator=(const fileMonitor&);
+
+
+public:
+
+    // Declare name of the class and its debug switch
+    ClassName("fileMonitor");
+
+    // Constructors
+
+        //- Construct null
+        fileMonitor();
+
+
+    // Destructor
+
+        ~fileMonitor();
+
+
+    // Member Functions
+
+        //- Add file to watch. Returns watch descriptor
+        label addWatch(const fileName&);
+
+        //- Remove file to watch. Return true if successful
+        bool removeWatch(const label watchFd);
+
+        //- Get name of file being watched
+        const fileName& getFile(const label watchFd) const;
+
+        //- Check state using handle
+        fileState getState(const label watchFd) const;
+
+        //- Check state of all files. Updates state_.
+        void updateStates(const bool syncPar) const;
+
+        //- Reset state (e.g. after having read it) using handle
+        void setUnmodified(const label watchFd);
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/db/IOobject/IOobject.C b/src/OpenFOAM/db/IOobject/IOobject.C
index b9a0a25893..77617b64fc 100644
--- a/src/OpenFOAM/db/IOobject/IOobject.C
+++ b/src/OpenFOAM/db/IOobject/IOobject.C
@@ -316,8 +316,12 @@ Foam::fileName Foam::IOobject::filePath() const
 
 Foam::Istream* Foam::IOobject::objectStream()
 {
-    fileName fName = filePath();
+    return objectStream(filePath());
+}
 
+
+Foam::Istream* Foam::IOobject::objectStream(const fileName& fName)
+{
     if (fName.size())
     {
         IFstream* isPtr = new IFstream(fName);
diff --git a/src/OpenFOAM/db/IOobject/IOobject.H b/src/OpenFOAM/db/IOobject/IOobject.H
index 32ce285bfd..4bb0a7c6c3 100644
--- a/src/OpenFOAM/db/IOobject/IOobject.H
+++ b/src/OpenFOAM/db/IOobject/IOobject.H
@@ -39,9 +39,16 @@ Description
     @param MUST_READ
         Object must be read from Istream on construction. \n
         Error if Istream does not exist or can't be read.
+        Does not check timestamp or re-read.
+    @param MUST_READ_IF_MODIFIED
+        Object must be read from Istream on construction. \n
+        Error if Istream does not exist or can't be read. If object is
+        registered its timestamp will be checked every timestep and possibly
+        re-read.
     @param READ_IF_PRESENT
         Read object from Istream if Istream exists, otherwise don't. \n
         Error only if Istream exists but can't be read.
+        Does not check timestamp or re-read.
     @param NO_READ
           Don't read
 
@@ -100,6 +107,7 @@ public:
         enum readOption
         {
             MUST_READ,
+            MUST_READ_IF_MODIFIED,
             READ_IF_PRESENT,
             NO_READ
         };
@@ -154,6 +162,10 @@ protected:
         //  The results is NULL if the stream construction failed
         Istream* objectStream();
 
+        //- Construct and return an IFstream for the object given the
+        //  exact file. The results is NULL if the stream construction failed
+        Istream* objectStream(const fileName&);
+
         //- Set the object state to bad
         void setBad(const string&);
 
diff --git a/src/OpenFOAM/db/IOobject/IOobjectReadHeader.C b/src/OpenFOAM/db/IOobject/IOobjectReadHeader.C
index fc85d5fa26..1f296fb7da 100644
--- a/src/OpenFOAM/db/IOobject/IOobjectReadHeader.C
+++ b/src/OpenFOAM/db/IOobject/IOobjectReadHeader.C
@@ -39,7 +39,7 @@ bool Foam::IOobject::readHeader(Istream& is)
     // Check Istream not already bad
     if (!is.good())
     {
-        if (rOpt_ == MUST_READ)
+        if (rOpt_ == MUST_READ || rOpt_ == MUST_READ_IF_MODIFIED)
         {
             FatalIOErrorIn("IOobject::readHeader(Istream&)", is)
                 << " stream not open for reading essential object from file "
@@ -102,7 +102,7 @@ bool Foam::IOobject::readHeader(Istream& is)
     }
     else
     {
-        if (rOpt_ == MUST_READ)
+        if (rOpt_ == MUST_READ || rOpt_ == MUST_READ_IF_MODIFIED)
         {
             FatalIOErrorIn("IOobject::readHeader(Istream&)", is)
                 << " stream failure while reading header"
diff --git a/src/OpenFOAM/db/IOobjects/IOField/IOField.C b/src/OpenFOAM/db/IOobjects/IOField/IOField.C
index 3b16672ea4..4af4f27073 100644
--- a/src/OpenFOAM/db/IOobjects/IOField/IOField.C
+++ b/src/OpenFOAM/db/IOobjects/IOField/IOField.C
@@ -32,9 +32,21 @@ Foam::IOField<Type>::IOField(const IOobject& io)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn("IOField::IOField(const IOobject&)")
+            << "IOField constructed with IOobject::MUST_READ_IF_MODIFIED"
+            " but IOField does not support automatic rereading."
+            << endl;
+    }
+
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -49,9 +61,21 @@ Foam::IOField<Type>::IOField(const IOobject& io, const label size)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn("IOField::IOField(const IOobject&, const label)")
+            << "IOField constructed with IOobject::MUST_READ_IF_MODIFIED"
+            " but IOField does not support automatic rereading."
+            << endl;
+    }
+
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -70,9 +94,21 @@ Foam::IOField<Type>::IOField(const IOobject& io, const Field<Type>& f)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn("IOField::IOField(const IOobject&, const Field<Type>&)")
+            << "IOField constructed with IOobject::MUST_READ_IF_MODIFIED"
+            " but IOField does not support automatic rereading."
+            << endl;
+    }
+
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -91,11 +127,25 @@ Foam::IOField<Type>::IOField(const IOobject& io, const Xfer<Field<Type> >& f)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn
+        (
+            "IOField::IOField(const IOobject&, const Xfer<Field<Type> >&)"
+        )   << "IOField constructed with IOobject::MUST_READ_IF_MODIFIED"
+            " but IOField does not support automatic rereading."
+            << endl;
+    }
+
     Field<Type>::transfer(f());
 
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
diff --git a/src/OpenFOAM/db/IOobjects/IOList/IOList.C b/src/OpenFOAM/db/IOobjects/IOList/IOList.C
index 39e0554b04..3e9b785607 100644
--- a/src/OpenFOAM/db/IOobjects/IOList/IOList.C
+++ b/src/OpenFOAM/db/IOobjects/IOList/IOList.C
@@ -32,9 +32,20 @@ Foam::IOList<T>::IOList(const IOobject& io)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn("IOList::IOList(const IOobject&)")
+            << "IOField constructed with IOobject::MUST_READ_IF_MODIFIED"
+            " but IOField does not support automatic rereading."
+            << endl;
+    }
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -49,9 +60,20 @@ Foam::IOList<T>::IOList(const IOobject& io, const label size)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn("IOList::IOList(const IOobject&, const label)")
+            << "IOField constructed with IOobject::MUST_READ_IF_MODIFIED"
+            " but IOField does not support automatic rereading."
+            << endl;
+    }
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -70,9 +92,21 @@ Foam::IOList<T>::IOList(const IOobject& io, const List<T>& list)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn("IOList::IOList(const IOobject&, const List<T>&)")
+            << "IOField constructed with IOobject::MUST_READ_IF_MODIFIED"
+            " but IOField does not support automatic rereading."
+            << endl;
+    }
+
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -91,11 +125,25 @@ Foam::IOList<T>::IOList(const IOobject& io, const Xfer<List<T> >& list)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn
+        (
+            "IOList::IOList(const IOobject&, const Xfer<List<T> >&)"
+        )   << "IOField constructed with IOobject::MUST_READ_IF_MODIFIED"
+            " but IOField does not support automatic rereading."
+            << endl;
+    }
+
     List<T>::transfer(list());
 
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
diff --git a/src/OpenFOAM/db/IOobjects/IOMap/IOMap.C b/src/OpenFOAM/db/IOobjects/IOMap/IOMap.C
index 54f3646b10..67d95333c4 100644
--- a/src/OpenFOAM/db/IOobjects/IOMap/IOMap.C
+++ b/src/OpenFOAM/db/IOobjects/IOMap/IOMap.C
@@ -34,7 +34,10 @@ Foam::IOMap<T>::IOMap(const IOobject& io)
 {
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -50,7 +53,10 @@ Foam::IOMap<T>::IOMap(const IOobject& io, const label size)
 {
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -71,7 +77,10 @@ Foam::IOMap<T>::IOMap(const IOobject& io, const Map<T>& map)
 {
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -94,7 +103,10 @@ Foam::IOMap<T>::IOMap(const IOobject& io, const Xfer<Map<T> >& map)
 
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
diff --git a/src/OpenFOAM/db/IOobjects/IOPtrList/IOPtrList.C b/src/OpenFOAM/db/IOobjects/IOPtrList/IOPtrList.C
index ad3ef2e4cd..565c77e0fb 100644
--- a/src/OpenFOAM/db/IOobjects/IOPtrList/IOPtrList.C
+++ b/src/OpenFOAM/db/IOobjects/IOPtrList/IOPtrList.C
@@ -35,7 +35,10 @@ Foam::IOPtrList<T>::IOPtrList(const IOobject& io, const INew& inewt)
 {
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -52,7 +55,10 @@ Foam::IOPtrList<T>::IOPtrList(const IOobject& io)
 {
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -84,7 +90,10 @@ Foam::IOPtrList<T>::IOPtrList(const IOobject& io, const PtrList<T>& list)
 {
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -107,7 +116,10 @@ Foam::IOPtrList<T>::IOPtrList(const IOobject& io, const Xfer<PtrList<T> >& list)
 
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
diff --git a/src/OpenFOAM/db/IOobjects/IOdictionary/IOdictionary.C b/src/OpenFOAM/db/IOobjects/IOdictionary/IOdictionary.C
index 136c6bbd18..c5a3778958 100644
--- a/src/OpenFOAM/db/IOobjects/IOdictionary/IOdictionary.C
+++ b/src/OpenFOAM/db/IOobjects/IOdictionary/IOdictionary.C
@@ -43,9 +43,24 @@ Foam::IOdictionary::IOdictionary(const IOobject& io)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ)
+    {
+        WarningIn("IOdictionary::IOdictionary(const IOobject&)")
+        //FatalErrorIn("IOdictionary::IOdictionary(const IOobject&)")
+            << "Dictionary constructed with IOobject::MUST_READ"
+            " instead of IOobject::MUST_READ_IF_MODIFIED." << nl
+            << "Use MUST_READ_IF_MODIFIED if you need automatic rereading."
+            << endl;
+            //<< abort(FatalError);
+    }
+
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -61,9 +76,24 @@ Foam::IOdictionary::IOdictionary(const IOobject& io, const dictionary& dict)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ)
+    {
+        WarningIn
+        (
+            "IOdictionary::IOdictionary(const IOobject& const dictionary&)"
+        )   << "Dictionary constructed with IOobject::MUST_READ"
+            " instead of IOobject::MUST_READ_IF_MODIFIED." << nl
+            << "Use MUST_READ_IF_MODIFIED if you need automatic rereading."
+            << endl;
+    }
+
     if
     (
-        io.readOpt() == IOobject::MUST_READ
+        (
+            io.readOpt() == IOobject::MUST_READ
+         || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
+        )
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
diff --git a/src/OpenFOAM/db/Time/Time.C b/src/OpenFOAM/db/Time/Time.C
index 0afa8d69b3..90772004e9 100644
--- a/src/OpenFOAM/db/Time/Time.C
+++ b/src/OpenFOAM/db/Time/Time.C
@@ -217,7 +217,7 @@ Foam::Time::Time
             controlDictName,
             system(),
             *this,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
@@ -242,6 +242,12 @@ Foam::Time::Time
     readLibs_(controlDict_, "libs"),
     functionObjects_(*this)
 {
+    // Time objects not registered so do like objectRegistry::checkIn ourselves.
+    if (runTimeModifiable_)
+    {
+        controlDict_.watchIndex() = addWatch(controlDict_.filePath());
+    }
+
     setControls();
 }
 
@@ -298,6 +304,13 @@ Foam::Time::Time
     readLibs_(controlDict_, "libs"),
     functionObjects_(*this)
 {
+
+    // Time objects not registered so do like objectRegistry::checkIn ourselves.
+    if (runTimeModifiable_)
+    {
+        controlDict_.watchIndex() = addWatch(controlDict_.filePath());
+    }
+
     setControls();
 }
 
@@ -365,6 +378,38 @@ Foam::Time::~Time()
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
+Foam::label Foam::Time::addWatch(const fileName& fName) const
+{
+    return monitor_.addWatch(fName);
+}
+
+
+bool Foam::Time::removeWatch(const label watchIndex) const
+{
+    return monitor_.removeWatch(watchIndex);
+}
+
+const Foam::fileName& Foam::Time::getFile(const label watchIndex) const
+{
+    return monitor_.getFile(watchIndex);
+}
+
+
+Foam::fileMonitor::fileState Foam::Time::getState
+(
+    const label watchFd
+) const
+{
+    return monitor_.getState(watchFd);
+}
+
+
+void Foam::Time::setUnmodified(const label watchFd) const
+{
+    monitor_.setUnmodified(watchFd);
+}
+
+
 Foam::word Foam::Time::timeName(const scalar t)
 {
     std::ostringstream buf;
diff --git a/src/OpenFOAM/db/Time/Time.H b/src/OpenFOAM/db/Time/Time.H
index 7596fee0c9..1021ba012e 100644
--- a/src/OpenFOAM/db/Time/Time.H
+++ b/src/OpenFOAM/db/Time/Time.H
@@ -51,6 +51,7 @@ SourceFiles
 #include "typeInfo.H"
 #include "dlLibraryTable.H"
 #include "functionObjectList.H"
+#include "fileMonitor.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -71,6 +72,9 @@ class Time
 {
     // Private data
 
+        //- file-change monitor for all registered files
+        mutable fileMonitor monitor_;
+
         //- The controlDict
         IOdictionary controlDict_;
 
@@ -275,11 +279,35 @@ public:
                 return graphFormat_;
             }
 
+            //- Supports re-reading
+            const Switch& runTimeModifiable() const
+            {
+                return runTimeModifiable_;
+            }
+
             //- Read control dictionary, update controls and time
             virtual bool read();
 
-            //- Read the objects that have been modified
-            void readModifiedObjects();
+            // Automatic rereading
+
+                //- Read the objects that have been modified
+                void readModifiedObjects();
+
+                //- Add watching of a file. Returns handle
+                label addWatch(const fileName&) const;
+
+                //- Remove watch on a file (using handle)
+                bool removeWatch(const label) const;
+
+                //- Get name of file being watched (using handle)
+                const fileName& getFile(const label) const;
+
+                //- Get current state of file (using handle)
+                fileMonitor::fileState getState(const label) const;
+
+                //- Set current state of file (using handle) to unmodified
+                void setUnmodified(const label) const;
+
 
             //- Return the location of "dir" containing the file "name".
             //  (eg, used in reading mesh data)
diff --git a/src/OpenFOAM/db/Time/TimeIO.C b/src/OpenFOAM/db/Time/TimeIO.C
index 11031875df..dd6d1e98ed 100644
--- a/src/OpenFOAM/db/Time/TimeIO.C
+++ b/src/OpenFOAM/db/Time/TimeIO.C
@@ -180,6 +180,11 @@ void Foam::Time::readDict()
 
     controlDict_.readIfPresent("graphFormat", graphFormat_);
     controlDict_.readIfPresent("runTimeModifiable", runTimeModifiable_);
+
+    if (!runTimeModifiable_ && controlDict_.watchIndex() != -1)
+    {
+        removeWatch(controlDict_.watchIndex());
+    }
 }
 
 
@@ -201,35 +206,28 @@ void Foam::Time::readModifiedObjects()
 {
     if (runTimeModifiable_)
     {
-        // For parallel runs check if any object's file has been modified
-        // and only call readIfModified on each object if this is the case
-        // to avoid unnecessary reductions in readIfModified for each object
+        // Get state of all monitored objects (=registered objects with a
+        // valid filePath).
+        // Note: requires same ordering in objectRegistries on different
+        // processors!
+        monitor_.updateStates(Pstream::parRun());
 
-        bool anyModified = true;
+//Pout<< "Time : runTimeModifiable_ and watchIndex:"
+//    << controlDict_.watchIndex() << endl;
 
-        if (Pstream::parRun())
+        // Time handling is special since controlDict_ is the one dictionary
+        // that is not registered to any database.
+
+        if (controlDict_.readIfModified())
         {
-            anyModified = controlDict_.modified() || objectRegistry::modified();
-            bool anyModifiedOnThisProc = anyModified;
-            reduce(anyModified, andOp<bool>());
-
-            if (anyModifiedOnThisProc && !anyModified)
-            {
-                WarningIn("Time::readModifiedObjects()")
-                    << "Delaying reading objects due to inconsistent "
-                       "file time-stamps between processors"
-                    << endl;
-            }
+           readDict();
+           functionObjects_.read();
         }
 
-        if (anyModified)
-        {
-            if (controlDict_.readIfModified())
-            {
-                readDict();
-                functionObjects_.read();
-            }
+        bool registryModified = objectRegistry::modified();
 
+        if (registryModified)
+        {
             objectRegistry::readModifiedObjects();
         }
     }
diff --git a/src/OpenFOAM/db/Time/findInstance.C b/src/OpenFOAM/db/Time/findInstance.C
index e588aeef4c..b41a6bb944 100644
--- a/src/OpenFOAM/db/Time/findInstance.C
+++ b/src/OpenFOAM/db/Time/findInstance.C
@@ -126,7 +126,11 @@ Foam::word Foam::Time::findInstance
                     << endl;
             }
 
-            if (rOpt == IOobject::MUST_READ)
+            if
+            (
+                rOpt == IOobject::MUST_READ
+             || rOpt == IOobject::MUST_READ_IF_MODIFIED
+            )
             {
                 FatalErrorIn
                 (
@@ -174,7 +178,7 @@ Foam::word Foam::Time::findInstance
         return constant();
     }
 
-    if (rOpt == IOobject::MUST_READ)
+    if (rOpt == IOobject::MUST_READ || rOpt == IOobject::MUST_READ_IF_MODIFIED)
     {
         FatalErrorIn
         (
diff --git a/src/OpenFOAM/db/functionObjects/IOOutputFilter/IOOutputFilter.H b/src/OpenFOAM/db/functionObjects/IOOutputFilter/IOOutputFilter.H
index b4e35c43a0..daef2de16f 100644
--- a/src/OpenFOAM/db/functionObjects/IOOutputFilter/IOOutputFilter.H
+++ b/src/OpenFOAM/db/functionObjects/IOOutputFilter/IOOutputFilter.H
@@ -90,7 +90,7 @@ public:
             const word& outputFilterName,
             const objectRegistry&,
             const fileName& dictName = OutputFilter::typeName() + "Dict",
-            const IOobject::readOption rOpt = IOobject::MUST_READ,
+            const IOobject::readOption rOpt = IOobject::MUST_READ_IF_MODIFIED,
             const bool loadFromFile = false
         );
 
diff --git a/src/OpenFOAM/db/objectRegistry/objectRegistry.C b/src/OpenFOAM/db/objectRegistry/objectRegistry.C
index 30ce98564d..6309714e1a 100644
--- a/src/OpenFOAM/db/objectRegistry/objectRegistry.C
+++ b/src/OpenFOAM/db/objectRegistry/objectRegistry.C
@@ -273,7 +273,7 @@ void Foam::objectRegistry::rename(const word& newName)
 
 bool Foam::objectRegistry::modified() const
 {
-    for (const_iterator iter = cbegin(); iter != cend(); ++iter)
+    forAllConstIter(HashTable<regIOobject*>, *this, iter)
     {
         if (iter()->modified())
         {
@@ -317,7 +317,7 @@ bool Foam::objectRegistry::writeObject
 {
     bool ok = true;
 
-    for (const_iterator iter = cbegin(); iter != cend(); ++iter)
+    forAllConstIter(HashTable<regIOobject*>, *this, iter)
     {
         if (objectRegistry::debug)
         {
diff --git a/src/OpenFOAM/db/objectRegistry/objectRegistry.H b/src/OpenFOAM/db/objectRegistry/objectRegistry.H
index 10165b3e97..512c1858ed 100644
--- a/src/OpenFOAM/db/objectRegistry/objectRegistry.H
+++ b/src/OpenFOAM/db/objectRegistry/objectRegistry.H
@@ -173,7 +173,6 @@ public:
             //- Remove an regIOobject from registry
             bool checkOut(regIOobject&) const;
 
-
         // Reading
 
             //- Return true if any of the object's files have been modified
diff --git a/src/OpenFOAM/db/regIOobject/regIOobject.C b/src/OpenFOAM/db/regIOobject/regIOobject.C
index 22244ff8ac..bdbd9468ce 100644
--- a/src/OpenFOAM/db/regIOobject/regIOobject.C
+++ b/src/OpenFOAM/db/regIOobject/regIOobject.C
@@ -45,7 +45,7 @@ Foam::regIOobject::regIOobject(const IOobject& io, const bool isTime)
     IOobject(io),
     registered_(false),
     ownedByRegistry_(false),
-    lastModified_(0),
+    watchIndex_(-1),
     eventNo_                // Do not get event for top level Time database
     (
         isTime
@@ -68,7 +68,7 @@ Foam::regIOobject::regIOobject(const regIOobject& rio)
     IOobject(rio),
     registered_(false),
     ownedByRegistry_(false),
-    lastModified_(rio.lastModified_),
+    watchIndex_(rio.watchIndex_),
     eventNo_(db().getEvent()),
     isPtr_(NULL)
 {
@@ -83,7 +83,7 @@ Foam::regIOobject::regIOobject(const regIOobject& rio, bool registerCopy)
     IOobject(rio),
     registered_(false),
     ownedByRegistry_(false),
-    lastModified_(rio.lastModified_),
+    watchIndex_(-1),
     eventNo_(db().getEvent()),
     isPtr_(NULL)
 {
@@ -133,6 +133,28 @@ bool Foam::regIOobject::checkIn()
         // any mapping
         registered_ = db().checkIn(*this);
 
+        if
+        (
+            registered_
+         && readOpt() == MUST_READ_IF_MODIFIED
+         && time().runTimeModifiable()
+        )
+        {
+            if (watchIndex_ != -1)
+            {
+                FatalErrorIn("regIOobject::checkIn()")
+                    << "Object " << objectPath()
+                    << " already watched with index " << watchIndex_
+                    << abort(FatalError);
+            }
+
+            fileName f = filePath();
+            if (f != fileName::null)
+            {
+                watchIndex_ = time().addWatch(f);
+            }
+        }
+
         // check-in on defaultRegion is allowed to fail, since subsetted meshes
         // are created with the same name as their originating mesh
         if (!registered_ && debug && name() != polyMesh::defaultRegion)
@@ -165,6 +187,12 @@ bool Foam::regIOobject::checkOut()
     if (registered_)
     {
         registered_ = false;
+
+        if (watchIndex_ != -1)
+        {
+            time().removeWatch(watchIndex_);
+            watchIndex_ = -1;
+        }
         return db().checkOut(*this);
     }
 
diff --git a/src/OpenFOAM/db/regIOobject/regIOobject.H b/src/OpenFOAM/db/regIOobject/regIOobject.H
index f3c2cc83f8..59e075420f 100644
--- a/src/OpenFOAM/db/regIOobject/regIOobject.H
+++ b/src/OpenFOAM/db/regIOobject/regIOobject.H
@@ -67,8 +67,8 @@ private:
         //- Is this object owned by the registry
         bool ownedByRegistry_;
 
-        //- Time of last modification
-        mutable time_t lastModified_;
+        //- Modification watch index
+        mutable label watchIndex_;
 
         //- eventNo of last update
         label eventNo_;
@@ -209,10 +209,17 @@ public:
             //- Read object
             virtual bool read();
 
-            //- Return true if the object's file has been modified
+            //- Return file-monitoring handle
+            inline label watchIndex() const;
+
+            //- Return file-monitoring handle
+            inline label& watchIndex();
+
+            //- Return true if the object's file (or files for objectRegistry)
+            //  have been modified. (modified state is cached by Time)
             virtual bool modified() const;
 
-            //- Read object if modified
+            //- Read object if modified (as set by call to modified)
             virtual bool readIfModified();
 
 
diff --git a/src/OpenFOAM/db/regIOobject/regIOobjectI.H b/src/OpenFOAM/db/regIOobject/regIOobjectI.H
index b092d0150d..47127ce868 100644
--- a/src/OpenFOAM/db/regIOobject/regIOobjectI.H
+++ b/src/OpenFOAM/db/regIOobject/regIOobjectI.H
@@ -90,4 +90,16 @@ inline Foam::label& Foam::regIOobject::eventNo()
 }
 
 
+inline Foam::label Foam::regIOobject::watchIndex() const
+{
+    return watchIndex_;
+}
+
+
+inline Foam::label& Foam::regIOobject::watchIndex()
+{
+    return watchIndex_;
+}
+
+
 // ************************************************************************* //
diff --git a/src/OpenFOAM/db/regIOobject/regIOobjectRead.C b/src/OpenFOAM/db/regIOobject/regIOobjectRead.C
index 42b43a51e5..0082c936c6 100644
--- a/src/OpenFOAM/db/regIOobject/regIOobjectRead.C
+++ b/src/OpenFOAM/db/regIOobject/regIOobjectRead.C
@@ -26,7 +26,7 @@ License
 #include "regIOobject.H"
 #include "IFstream.H"
 #include "Time.H"
-#include "PstreamReduceOps.H"
+//#include "PstreamReduceOps.H"
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
@@ -52,14 +52,26 @@ Foam::Istream& Foam::regIOobject::readStream()
     // Construct object stream and read header if not already constructed
     if (!isPtr_)
     {
-        if (!(isPtr_ = objectStream()))
+
+        fileName objPath;
+        if (watchIndex_ != -1)
+        {
+            // File is being watched. Read exact file that is being watched.
+            objPath = time().getFile(watchIndex_);
+        }
+        else
+        {
+            objPath = filePath();
+        }
+
+        if (!(isPtr_ = objectStream(objPath)))
         {
             FatalIOError
             (
                 "regIOobject::readStream()",
                 __FILE__,
                 __LINE__,
-                objectPath(),
+                objPath,
                 0
             )   << "cannot open file"
                 << exit(FatalIOError);
@@ -72,9 +84,10 @@ Foam::Istream& Foam::regIOobject::readStream()
         }
     }
 
-    if (!lastModified_)
+    // Mark as uptodate if read succesfully
+    if (watchIndex_ != -1)
     {
-        lastModified_ = lastModified(filePath());
+        time().setUnmodified(watchIndex_);
     }
 
     return *isPtr_;
@@ -151,49 +164,27 @@ bool Foam::regIOobject::read()
 
 bool Foam::regIOobject::modified() const
 {
-    return
-    (
-        lastModified_
-     && lastModified(filePath()) > (lastModified_ + fileModificationSkew)
-    );
+    if (watchIndex_ != -1)
+    {
+        return time().getState(watchIndex_) != fileMonitor::UNMODIFIED;
+    }
+    else
+    {
+        return false;
+    }
 }
 
 
 bool Foam::regIOobject::readIfModified()
 {
-    if (lastModified_)
+    if (watchIndex_ != -1)
     {
-        time_t newTimeStamp = lastModified(filePath());
-
-        bool readFile = false;
-
-        if (newTimeStamp > (lastModified_ + fileModificationSkew))
+        if (modified())
         {
-            readFile = true;
-        }
-
-        if (Pstream::parRun())
-        {
-            bool readFileOnThisProc = readFile;
-            reduce(readFile, andOp<bool>());
-
-            if (readFileOnThisProc && !readFile)
-            {
-                WarningIn("regIOobject::readIfModified()")
-                    << "Delaying reading " << name()
-                    << " of class " << headerClassName()
-                    << " due to inconsistent "
-                       "file time-stamps between processors"
-                    << endl;
-            }
-        }
-
-        if (readFile)
-        {
-            lastModified_ = newTimeStamp;
+            const fileName& fName = time().getFile(watchIndex_);
             Info<< "regIOobject::readIfModified() : " << nl
-                << "    Reading object " << name()
-                << " from file " << filePath() << endl;
+                << "    Re-reading object " << name()
+                << " from file " << fName << endl;
             return read();
         }
         else
diff --git a/src/OpenFOAM/db/regIOobject/regIOobjectWrite.C b/src/OpenFOAM/db/regIOobject/regIOobjectWrite.C
index 1f2c174fb4..8c03003e82 100644
--- a/src/OpenFOAM/db/regIOobject/regIOobjectWrite.C
+++ b/src/OpenFOAM/db/regIOobject/regIOobjectWrite.C
@@ -114,9 +114,9 @@ bool Foam::regIOobject::writeObject
 
     // Only update the lastModified_ time if this object is re-readable,
     // i.e. lastModified_ is already set
-    if (lastModified_)
+    if (watchIndex_ != -1)
     {
-        lastModified_ = lastModified(objectPath());
+        time().setUnmodified(watchIndex_);
     }
 
     return osGood;
diff --git a/src/OpenFOAM/fields/GeometricFields/GeometricField/GeometricField.C b/src/OpenFOAM/fields/GeometricFields/GeometricField/GeometricField.C
index f420291fd6..286d1721be 100644
--- a/src/OpenFOAM/fields/GeometricFields/GeometricField/GeometricField.C
+++ b/src/OpenFOAM/fields/GeometricFields/GeometricField/GeometricField.C
@@ -112,12 +112,16 @@ Foam::GeometricField<Type, PatchField, GeoMesh>::readField(Istream& is)
 template<class Type, template<class> class PatchField, class GeoMesh>
 bool Foam::GeometricField<Type, PatchField, GeoMesh>::readIfPresent()
 {
-    if (this->readOpt() == IOobject::MUST_READ)
+    if
+    (
+        this->readOpt() == IOobject::MUST_READ
+     || this->readOpt() == IOobject::MUST_READ_IF_MODIFIED
+    )
     {
         WarningIn
         (
             "GeometricField<Type, PatchField, GeoMesh>::readIfPresent()"
-        )   << "read option IOobject::MUST_READ "
+        )   << "read option IOobject::MUST_READ or MUST_READ_IF_MODIFIED"
             << "suggests that a read constructor for field " << this->name()
             << " would be more appropriate." << endl;
     }
diff --git a/src/OpenFOAM/matrices/solution/solution.C b/src/OpenFOAM/matrices/solution/solution.C
index 5aa40ae572..71359e5dab 100644
--- a/src/OpenFOAM/matrices/solution/solution.C
+++ b/src/OpenFOAM/matrices/solution/solution.C
@@ -54,7 +54,7 @@ Foam::solution::solution(const objectRegistry& obr, const fileName& dictName)
             dictName,
             obr.time().system(),
             obr,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/OpenFOAM/matrices/tolerances/tolerances.C b/src/OpenFOAM/matrices/tolerances/tolerances.C
index 9becd91b60..ff70e0b93a 100644
--- a/src/OpenFOAM/matrices/tolerances/tolerances.C
+++ b/src/OpenFOAM/matrices/tolerances/tolerances.C
@@ -36,7 +36,7 @@ Foam::tolerances::tolerances(const Time& t, const fileName& dictName)
             dictName,
             t.system(),
             t,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C b/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C
index f23a05879f..3a1ff00b32 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C
+++ b/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C
@@ -62,8 +62,27 @@ Foam::polyBoundaryMesh::polyBoundaryMesh
     regIOobject(io),
     mesh_(mesh)
 {
-    if (readOpt() == IOobject::MUST_READ)
+    if
+    (
+        readOpt() == IOobject::MUST_READ
+     || readOpt() == IOobject::MUST_READ_IF_MODIFIED
+    )
     {
+        if (readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+        {
+            WarningIn
+            (
+                "polyBoundaryMesh::polyBoundaryMesh\n"
+                "(\n"
+                "    const IOobject&,\n"
+                "    const polyMesh&\n"
+                ")"
+            )   << "Specified IOobject::MUST_READ_IF_MODIFIED but class"
+                << " does not support automatic rereading."
+                << endl;
+        }
+
+
         polyPatchList& patches = *this;
 
         // Read polyPatchList
diff --git a/src/OpenFOAM/meshes/polyMesh/zones/ZoneMesh/ZoneMesh.C b/src/OpenFOAM/meshes/polyMesh/zones/ZoneMesh/ZoneMesh.C
index fe1c6de03e..babb31b6e8 100644
--- a/src/OpenFOAM/meshes/polyMesh/zones/ZoneMesh/ZoneMesh.C
+++ b/src/OpenFOAM/meshes/polyMesh/zones/ZoneMesh/ZoneMesh.C
@@ -86,9 +86,24 @@ Foam::ZoneMesh<ZoneType, MeshType>::ZoneMesh
     if
     (
         readOpt() == IOobject::MUST_READ
+     || readOpt() == IOobject::MUST_READ_IF_MODIFIED
      || (readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
+        if (readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+        {
+            WarningIn
+            (
+                "ZoneMesh::ZoneMesh\n"
+                "(\n"
+                "    const IOobject&,\n"
+                "    const MeshType&\n"
+                ")"
+            )   << "Specified IOobject::MUST_READ_IF_MODIFIED but class"
+                << " does not support automatic rereading."
+                << endl;
+        }
+
         PtrList<ZoneType>& zones = *this;
 
         // Read zones
diff --git a/src/dynamicFvMesh/dynamicFvMesh/dynamicFvMeshNew.C b/src/dynamicFvMesh/dynamicFvMesh/dynamicFvMeshNew.C
index 9a4c920dfa..a37db88c69 100644
--- a/src/dynamicFvMesh/dynamicFvMesh/dynamicFvMeshNew.C
+++ b/src/dynamicFvMesh/dynamicFvMesh/dynamicFvMeshNew.C
@@ -39,7 +39,7 @@ Foam::autoPtr<Foam::dynamicFvMesh> Foam::dynamicFvMesh::New(const IOobject& io)
             "dynamicMeshDict",
             io.time().constant(),
             io.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/src/dynamicFvMesh/dynamicInkJetFvMesh/dynamicInkJetFvMesh.C b/src/dynamicFvMesh/dynamicInkJetFvMesh/dynamicInkJetFvMesh.C
index cd937135fd..18e4a32d78 100644
--- a/src/dynamicFvMesh/dynamicInkJetFvMesh/dynamicInkJetFvMesh.C
+++ b/src/dynamicFvMesh/dynamicInkJetFvMesh/dynamicInkJetFvMesh.C
@@ -51,8 +51,9 @@ Foam::dynamicInkJetFvMesh::dynamicInkJetFvMesh(const IOobject& io)
                 "dynamicMeshDict",
                 io.time().constant(),
                 *this,
-                IOobject::MUST_READ,
-                IOobject::NO_WRITE
+                IOobject::MUST_READ_IF_MODIFIED,
+                IOobject::NO_WRITE,
+                false
             )
         ).subDict(typeName + "Coeffs")
     ),
diff --git a/src/dynamicFvMesh/dynamicRefineFvMesh/dynamicRefineFvMesh.C b/src/dynamicFvMesh/dynamicRefineFvMesh/dynamicRefineFvMesh.C
index 5ecd3efdb9..5e992af101 100644
--- a/src/dynamicFvMesh/dynamicRefineFvMesh/dynamicRefineFvMesh.C
+++ b/src/dynamicFvMesh/dynamicRefineFvMesh/dynamicRefineFvMesh.C
@@ -179,7 +179,7 @@ void Foam::dynamicRefineFvMesh::readDict()
                 "dynamicMeshDict",
                 time().constant(),
                 *this,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
@@ -1016,7 +1016,7 @@ bool Foam::dynamicRefineFvMesh::update()
                 "dynamicMeshDict",
                 time().constant(),
                 *this,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/dynamicFvMesh/solidBodyMotionFvMesh/solidBodyMotionFvMesh.C b/src/dynamicFvMesh/solidBodyMotionFvMesh/solidBodyMotionFvMesh.C
index 420304ecf7..88b7e521c0 100644
--- a/src/dynamicFvMesh/solidBodyMotionFvMesh/solidBodyMotionFvMesh.C
+++ b/src/dynamicFvMesh/solidBodyMotionFvMesh/solidBodyMotionFvMesh.C
@@ -51,8 +51,9 @@ Foam::solidBodyMotionFvMesh::solidBodyMotionFvMesh(const IOobject& io)
                 "dynamicMeshDict",
                 io.time().constant(),
                 *this,
-                IOobject::MUST_READ,
-                IOobject::NO_WRITE
+                IOobject::MUST_READ_IF_MODIFIED,
+                IOobject::NO_WRITE,
+                false
             )
         ).subDict(typeName + "Coeffs")
     ),
diff --git a/src/dynamicMesh/motionSolver/motionSolver.C b/src/dynamicMesh/motionSolver/motionSolver.C
index efc29c2afc..a225c4430e 100644
--- a/src/dynamicMesh/motionSolver/motionSolver.C
+++ b/src/dynamicMesh/motionSolver/motionSolver.C
@@ -47,7 +47,7 @@ Foam::motionSolver::motionSolver(const polyMesh& mesh)
             "dynamicMeshDict",
             mesh.time().constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
@@ -67,7 +67,7 @@ Foam::autoPtr<Foam::motionSolver> Foam::motionSolver::New(const polyMesh& mesh)
             "dynamicMeshDict",
             mesh.time().constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/refinementHistory.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/refinementHistory.C
index 744fceb2d5..9450b2c717 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/refinementHistory.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/refinementHistory.C
@@ -331,9 +331,21 @@ Foam::refinementHistory::refinementHistory(const IOobject& io)
 :
     regIOobject(io)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn
+        (
+            "refinementHistory::refinementHistory(const IOobject&)"
+        )   << "Specified IOobject::MUST_READ_IF_MODIFIED but class"
+            << " does not support automatic rereading."
+            << endl;
+    }
+
     if
     (
         io.readOpt() == IOobject::MUST_READ
+     || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -365,9 +377,22 @@ Foam::refinementHistory::refinementHistory
     freeSplitCells_(0),
     visibleCells_(visibleCells)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn
+        (
+            "refinementHistory::refinementHistory"
+            "(const IOobject&, const List<splitCell8>&, const labelList&)"
+        )   << "Specified IOobject::MUST_READ_IF_MODIFIED but class"
+            << " does not support automatic rereading."
+            << endl;
+    }
+
     if
     (
         io.readOpt() == IOobject::MUST_READ
+     || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
@@ -399,9 +424,22 @@ Foam::refinementHistory::refinementHistory
     regIOobject(io),
     freeSplitCells_(0)
 {
+    // Temporary warning
+    if (io.readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+    {
+        WarningIn
+        (
+            "refinementHistory::refinementHistory"
+            "(const IOobject&, const label)"
+        )   << "Specified IOobject::MUST_READ_IF_MODIFIED but class"
+            << " does not support automatic rereading."
+            << endl;
+    }
+
     if
     (
         io.readOpt() == IOobject::MUST_READ
+     || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChanger/polyTopoChanger.C b/src/dynamicMesh/polyTopoChange/polyTopoChanger/polyTopoChanger.C
index 1f7de13aba..dcb9534417 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChanger/polyTopoChanger.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChanger/polyTopoChanger.C
@@ -43,9 +43,19 @@ void Foam::polyTopoChanger::readModifiers()
     if
     (
         readOpt() == IOobject::MUST_READ
+     || readOpt() == IOobject::MUST_READ_IF_MODIFIED
      || (readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
+        if (readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+        {
+            WarningIn("polyTopoChanger::readModifiers()")
+                << "Specified IOobject::MUST_READ_IF_MODIFIED but class"
+                << " does not support automatic rereading."
+                << endl;
+        }
+
+
         PtrList<polyMeshModifier>& modifiers = *this;
 
         // Read modifiers
diff --git a/src/edgeMesh/featureEdgeMesh/featureEdgeMesh.C b/src/edgeMesh/featureEdgeMesh/featureEdgeMesh.C
index 4fe2165606..d8637404cb 100644
--- a/src/edgeMesh/featureEdgeMesh/featureEdgeMesh.C
+++ b/src/edgeMesh/featureEdgeMesh/featureEdgeMesh.C
@@ -40,9 +40,19 @@ Foam::featureEdgeMesh::featureEdgeMesh(const IOobject& io)
     if
     (
         io.readOpt() == IOobject::MUST_READ
+     || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
+        if (readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+        {
+            WarningIn("featureEdgeMesh::featureEdgeMesh(const IOobject&)")
+                << "Specified IOobject::MUST_READ_IF_MODIFIED but class"
+                << " does not support automatic rereading."
+                << endl;
+        }
+
+
         readStream(typeName) >> *this;
         close();
     }
@@ -82,9 +92,19 @@ Foam::featureEdgeMesh::featureEdgeMesh
     if
     (
         io.readOpt() == IOobject::MUST_READ
+     || io.readOpt() == IOobject::MUST_READ_IF_MODIFIED
      || (io.readOpt() == IOobject::READ_IF_PRESENT && headerOk())
     )
     {
+        if (readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+        {
+            WarningIn("featureEdgeMesh::featureEdgeMesh(const IOobject&)")
+                << "Specified IOobject::MUST_READ_IF_MODIFIED but class"
+                << " does not support automatic rereading."
+                << endl;
+        }
+
+
         readStream(typeName) >> *this;
         close();
     }
diff --git a/src/engine/engineMesh/engineMesh/engineMeshNew.C b/src/engine/engineMesh/engineMesh/engineMeshNew.C
index b827036fd3..d34b881cc9 100644
--- a/src/engine/engineMesh/engineMesh/engineMeshNew.C
+++ b/src/engine/engineMesh/engineMesh/engineMeshNew.C
@@ -44,7 +44,7 @@ Foam::autoPtr<Foam::engineMesh> Foam::engineMesh::New
                 "engineGeometry",
                 io.time().constant(),
                 io.db(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/engine/engineTime/engineTime.C b/src/engine/engineTime/engineTime.C
index 822f8224a8..2f9ec62313 100644
--- a/src/engine/engineTime/engineTime.C
+++ b/src/engine/engineTime/engineTime.C
@@ -72,7 +72,7 @@ Foam::engineTime::engineTime
             "engineGeometry",
             constant(),
             *this,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/src/finiteVolume/cfdTools/general/MRF/MRFZones.C b/src/finiteVolume/cfdTools/general/MRF/MRFZones.C
index 5ceb48af51..cf7bdc8ff8 100644
--- a/src/finiteVolume/cfdTools/general/MRF/MRFZones.C
+++ b/src/finiteVolume/cfdTools/general/MRF/MRFZones.C
@@ -45,7 +45,7 @@ Foam::MRFZones::MRFZones(const fvMesh& mesh)
             "MRFZones",
             mesh.time().constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         ),
         MRFZone::iNew(mesh)
diff --git a/src/finiteVolume/cfdTools/general/SRF/SRFModel/SRFModel/SRFModel.C b/src/finiteVolume/cfdTools/general/SRF/SRFModel/SRFModel/SRFModel.C
index 626718c932..e753196cde 100644
--- a/src/finiteVolume/cfdTools/general/SRF/SRFModel/SRFModel/SRFModel.C
+++ b/src/finiteVolume/cfdTools/general/SRF/SRFModel/SRFModel/SRFModel.C
@@ -53,7 +53,7 @@ Foam::SRF::SRFModel::SRFModel
             "SRFProperties",
             Urel.time().constant(),
             Urel.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/finiteVolume/cfdTools/general/SRF/SRFModel/SRFModel/SRFModelNew.C b/src/finiteVolume/cfdTools/general/SRF/SRFModel/SRFModel/SRFModelNew.C
index 5c2eb2ea76..20d358235b 100644
--- a/src/finiteVolume/cfdTools/general/SRF/SRFModel/SRFModel/SRFModelNew.C
+++ b/src/finiteVolume/cfdTools/general/SRF/SRFModel/SRFModel/SRFModelNew.C
@@ -43,7 +43,7 @@ Foam::autoPtr<Foam::SRF::SRFModel> Foam::SRF::SRFModel::New
                 "SRFProperties",
                 Urel.time().constant(),
                 Urel.db(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/finiteVolume/cfdTools/general/fieldSources/pressureGradientExplicitSource/pressureGradientExplicitSource.C b/src/finiteVolume/cfdTools/general/fieldSources/pressureGradientExplicitSource/pressureGradientExplicitSource.C
index 6f5af3bfab..b4351f34c7 100644
--- a/src/finiteVolume/cfdTools/general/fieldSources/pressureGradientExplicitSource/pressureGradientExplicitSource.C
+++ b/src/finiteVolume/cfdTools/general/fieldSources/pressureGradientExplicitSource/pressureGradientExplicitSource.C
@@ -70,7 +70,7 @@ Foam::pressureGradientExplicitSource::pressureGradientExplicitSource
             sourceName + "Properties",
             mesh_.time().constant(),
             mesh_,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/finiteVolume/finiteVolume/fvSchemes/fvSchemes.C b/src/finiteVolume/finiteVolume/fvSchemes/fvSchemes.C
index e77b6c77a0..37b09def99 100644
--- a/src/finiteVolume/finiteVolume/fvSchemes/fvSchemes.C
+++ b/src/finiteVolume/finiteVolume/fvSchemes/fvSchemes.C
@@ -64,7 +64,7 @@ Foam::fvSchemes::fvSchemes(const objectRegistry& obr)
             "fvSchemes",
             obr.time().system(),
             obr,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/fvMotionSolver/fvMotionSolvers/displacement/interpolation/displacementInterpolationFvMotionSolver.C b/src/fvMotionSolver/fvMotionSolvers/displacement/interpolation/displacementInterpolationFvMotionSolver.C
index 977fdb89a0..e1613e584d 100644
--- a/src/fvMotionSolver/fvMotionSolvers/displacement/interpolation/displacementInterpolationFvMotionSolver.C
+++ b/src/fvMotionSolver/fvMotionSolvers/displacement/interpolation/displacementInterpolationFvMotionSolver.C
@@ -70,7 +70,7 @@ displacementInterpolationFvMotionSolver
                 "dynamicMeshDict",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/lagrangian/basic/Cloud/CloudIO.C b/src/lagrangian/basic/Cloud/CloudIO.C
index 9b4bf0d618..388fba1c57 100644
--- a/src/lagrangian/basic/Cloud/CloudIO.C
+++ b/src/lagrangian/basic/Cloud/CloudIO.C
@@ -45,7 +45,7 @@ void Foam::Cloud<ParticleType>::readCloudUniformProperties()
         time().timeName(),
         "uniform"/cloud::prefix/name(),
         db(),
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE,
         false
     );
diff --git a/src/lagrangian/dieselSpray/spray/spray.C b/src/lagrangian/dieselSpray/spray/spray.C
index 4f98523b07..6ff9319f9a 100644
--- a/src/lagrangian/dieselSpray/spray/spray.C
+++ b/src/lagrangian/dieselSpray/spray/spray.C
@@ -83,7 +83,7 @@ Foam::spray::spray
             "sprayProperties",
             U.time().constant(),
             U.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
@@ -98,7 +98,7 @@ Foam::spray::spray
             "injectorProperties",
             U.time().constant(),
             U.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         ),
         injector::iNew(U.time())
diff --git a/src/lagrangian/dsmc/clouds/Templates/DsmcCloud/DsmcCloud.C b/src/lagrangian/dsmc/clouds/Templates/DsmcCloud/DsmcCloud.C
index 455ee7936d..e748f72077 100644
--- a/src/lagrangian/dsmc/clouds/Templates/DsmcCloud/DsmcCloud.C
+++ b/src/lagrangian/dsmc/clouds/Templates/DsmcCloud/DsmcCloud.C
@@ -611,7 +611,7 @@ Foam::DsmcCloud<ParcelType>::DsmcCloud
             cloudName + "Properties",
             mesh_.time().constant(),
             mesh_,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
@@ -833,7 +833,7 @@ Foam::DsmcCloud<ParcelType>::DsmcCloud
             cloudName + "Properties",
             mesh_.time().constant(),
             mesh_,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/lagrangian/intermediate/clouds/Templates/KinematicCloud/KinematicCloud.C b/src/lagrangian/intermediate/clouds/Templates/KinematicCloud/KinematicCloud.C
index 7fc3cf8636..10fccde371 100644
--- a/src/lagrangian/intermediate/clouds/Templates/KinematicCloud/KinematicCloud.C
+++ b/src/lagrangian/intermediate/clouds/Templates/KinematicCloud/KinematicCloud.C
@@ -181,7 +181,7 @@ Foam::KinematicCloud<ParcelType>::KinematicCloud
             cloudName + "Properties",
             rho.mesh().time().constant(),
             rho.mesh(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectionModel/InjectionModel.C b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectionModel/InjectionModel.C
index 9b44324461..c56ff29618 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectionModel/InjectionModel.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectionModel/InjectionModel.C
@@ -40,7 +40,7 @@ void Foam::InjectionModel<CloudType>::readProps()
         owner_.db().time().timeName(),
         "uniform"/cloud::prefix/owner_.name(),
         owner_.db(),
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE,
         false
     );
diff --git a/src/lagrangian/molecularDynamics/molecule/mdTools/createAutoCorrelationFunctions.H b/src/lagrangian/molecularDynamics/molecule/mdTools/createAutoCorrelationFunctions.H
index ebe1781e6f..b257b7eece 100644
--- a/src/lagrangian/molecularDynamics/molecule/mdTools/createAutoCorrelationFunctions.H
+++ b/src/lagrangian/molecularDynamics/molecule/mdTools/createAutoCorrelationFunctions.H
@@ -32,7 +32,7 @@ IOdictionary mdTransportProperitesDict
         "mdTransportProperitesDict",
         mesh.time().system(),
         mesh,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE,
         false
     )
diff --git a/src/lagrangian/molecularDynamics/molecule/moleculeCloud/moleculeCloud.C b/src/lagrangian/molecularDynamics/molecule/moleculeCloud/moleculeCloud.C
index 55f24f100f..5fef0b1d0d 100644
--- a/src/lagrangian/molecularDynamics/molecule/moleculeCloud/moleculeCloud.C
+++ b/src/lagrangian/molecularDynamics/molecule/moleculeCloud/moleculeCloud.C
@@ -56,7 +56,7 @@ void Foam::moleculeCloud::buildConstProps()
             "moleculeProperties",
             mesh_.time().constant(),
             mesh_,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/src/lagrangian/molecularDynamics/potential/potential/potential.C b/src/lagrangian/molecularDynamics/potential/potential/potential.C
index a54ef7f153..f9d8dd683c 100644
--- a/src/lagrangian/molecularDynamics/potential/potential/potential.C
+++ b/src/lagrangian/molecularDynamics/potential/potential/potential.C
@@ -104,7 +104,7 @@ void Foam::potential::potential::readPotentialDict()
             "idList",
             mesh_.time().constant(),
             mesh_,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
@@ -120,7 +120,7 @@ void Foam::potential::potential::readPotentialDict()
                 "moleculeProperties",
                 mesh_.time().constant(),
                 mesh_,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
@@ -151,7 +151,7 @@ void Foam::potential::potential::readPotentialDict()
             "potentialDict",
             mesh_.time().system(),
             mesh_,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
@@ -260,7 +260,7 @@ void Foam::potential::potential::readMdInitialiseDict
             "moleculeProperties",
             mesh_.time().constant(),
             mesh_,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/src/lagrangian/solidParticle/solidParticleCloud.C b/src/lagrangian/solidParticle/solidParticleCloud.C
index 753b760b14..625116d525 100644
--- a/src/lagrangian/solidParticle/solidParticleCloud.C
+++ b/src/lagrangian/solidParticle/solidParticleCloud.C
@@ -54,7 +54,7 @@ Foam::solidParticleCloud::solidParticleCloud
             "particleProperties",
             mesh_.time().constant(),
             mesh_,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/meshTools/searchableSurface/distributedTriSurfaceMesh.C b/src/meshTools/searchableSurface/distributedTriSurfaceMesh.C
index 70bfa897a9..a046f05050 100644
--- a/src/meshTools/searchableSurface/distributedTriSurfaceMesh.C
+++ b/src/meshTools/searchableSurface/distributedTriSurfaceMesh.C
@@ -838,7 +838,7 @@ Foam::distributedTriSurfaceMesh::independentlyDistributedBbs
                 "decomposeParDict",
                 searchableSurface::time().system(),
                 searchableSurface::time(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/meshTools/sets/cellSources/fieldToCell/fieldToCell.C b/src/meshTools/sets/cellSources/fieldToCell/fieldToCell.C
index 96ce8b6cbe..b934db15ef 100644
--- a/src/meshTools/sets/cellSources/fieldToCell/fieldToCell.C
+++ b/src/meshTools/sets/cellSources/fieldToCell/fieldToCell.C
@@ -189,7 +189,8 @@ void Foam::fieldToCell::applyToSet
         mesh().time().timeName(),
         mesh(),
         IOobject::MUST_READ,
-        IOobject::AUTO_WRITE
+        IOobject::AUTO_WRITE,
+        false
     );
 
     if (!fieldObject.headerOk())
diff --git a/src/meshTools/sets/topoSets/cellZoneSet.C b/src/meshTools/sets/topoSets/cellZoneSet.C
index 0a387c669f..70de4a799c 100644
--- a/src/meshTools/sets/topoSets/cellZoneSet.C
+++ b/src/meshTools/sets/topoSets/cellZoneSet.C
@@ -80,6 +80,7 @@ cellZoneSet::cellZoneSet
     if
     (
         (r == IOobject::MUST_READ)
+     || (r == IOobject::MUST_READ_IF_MODIFIED)
      || (r == IOobject::READ_IF_PRESENT && zoneID != -1)
     )
     {
diff --git a/src/meshTools/sets/topoSets/faceZoneSet.C b/src/meshTools/sets/topoSets/faceZoneSet.C
index ed552af24b..00669101c8 100644
--- a/src/meshTools/sets/topoSets/faceZoneSet.C
+++ b/src/meshTools/sets/topoSets/faceZoneSet.C
@@ -82,6 +82,7 @@ faceZoneSet::faceZoneSet
     if
     (
         (r == IOobject::MUST_READ)
+     || (r == IOobject::MUST_READ_IF_MODIFIED)
      || (r == IOobject::READ_IF_PRESENT && zoneID != -1)
     )
     {
diff --git a/src/meshTools/sets/topoSets/pointZoneSet.C b/src/meshTools/sets/topoSets/pointZoneSet.C
index 64c1a29ed1..00870ee652 100644
--- a/src/meshTools/sets/topoSets/pointZoneSet.C
+++ b/src/meshTools/sets/topoSets/pointZoneSet.C
@@ -81,7 +81,8 @@ pointZoneSet::pointZoneSet
 
     if
     (
-        (r == IOobject::MUST_READ)
+        r == IOobject::MUST_READ
+     || r == IOobject::MUST_READ_IF_MODIFIED
      || (r == IOobject::READ_IF_PRESENT && zoneID != -1)
     )
     {
diff --git a/src/meshTools/sets/topoSets/topoSet.C b/src/meshTools/sets/topoSets/topoSet.C
index fb9e79164b..b4530e5b6e 100644
--- a/src/meshTools/sets/topoSets/topoSet.C
+++ b/src/meshTools/sets/topoSets/topoSet.C
@@ -309,6 +309,7 @@ Foam::topoSet::topoSet(const IOobject& obj, const word& wantedType)
     if
     (
         readOpt() == IOobject::MUST_READ
+     || readOpt() == IOobject::MUST_READ_IF_MODIFIED
      || (
             readOpt() == IOobject::READ_IF_PRESENT
          && headerOk()
@@ -356,6 +357,7 @@ Foam::topoSet::topoSet
     if
     (
         readOpt() == IOobject::MUST_READ
+     || readOpt() == IOobject::MUST_READ_IF_MODIFIED
      || (
             readOpt() == IOobject::READ_IF_PRESENT
          && headerOk()
diff --git a/src/postProcessing/functionObjects/field/fieldAverage/fieldAverage/fieldAverage.C b/src/postProcessing/functionObjects/field/fieldAverage/fieldAverage/fieldAverage.C
index a47a8b83cc..f27a3f8f49 100644
--- a/src/postProcessing/functionObjects/field/fieldAverage/fieldAverage/fieldAverage.C
+++ b/src/postProcessing/functionObjects/field/fieldAverage/fieldAverage/fieldAverage.C
@@ -258,7 +258,7 @@ void Foam::fieldAverage::readAveragingProperties()
             obr_.time().timeName(),
             "uniform",
             obr_,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         );
diff --git a/src/postProcessing/functionObjects/field/fieldValues/cellSource/cellSource.C b/src/postProcessing/functionObjects/field/fieldValues/cellSource/cellSource.C
index 7f20d75047..51f08c461e 100644
--- a/src/postProcessing/functionObjects/field/fieldValues/cellSource/cellSource.C
+++ b/src/postProcessing/functionObjects/field/fieldValues/cellSource/cellSource.C
@@ -32,11 +32,11 @@ License
 defineTypeNameAndDebug(Foam::fieldValues::cellSource, 0);
 
 template<>
-const char* NamedEnum<fieldValues::cellSource::sourceType, 2>::
+const char* Foam::NamedEnum<Foam::fieldValues::cellSource::sourceType, 2>::
 names[] = {"cellZone", "all"};
 
-const NamedEnum<fieldValues::cellSource::sourceType, 2>
-    fieldValues::cellSource::sourceTypeNames_;
+const Foam::NamedEnum<Foam::fieldValues::cellSource::sourceType, 2>
+    Foam::fieldValues::cellSource::sourceTypeNames_;
 
 template<>
 const char* Foam::NamedEnum<Foam::fieldValues::cellSource::operationType, 7>::
diff --git a/src/postProcessing/functionObjects/field/fieldValues/cellSource/cellSource.H b/src/postProcessing/functionObjects/field/fieldValues/cellSource/cellSource.H
index 44f836428a..c3a033f644 100644
--- a/src/postProcessing/functionObjects/field/fieldValues/cellSource/cellSource.H
+++ b/src/postProcessing/functionObjects/field/fieldValues/cellSource/cellSource.H
@@ -94,7 +94,7 @@ public:
         };
 
         //- Source type names
-        static const NamedEnum<sourceType, 1> sourceTypeNames_;
+        static const NamedEnum<sourceType, 2> sourceTypeNames_;
 
 
         //- Operation type enumeration
diff --git a/src/sampling/include/buildPatch.H b/src/sampling/include/buildPatch.H
index 0d6338ebb0..e355d79490 100644
--- a/src/sampling/include/buildPatch.H
+++ b/src/sampling/include/buildPatch.H
@@ -6,7 +6,7 @@ IOdictionary planeToPatchDict
         "planeToPatchDict",
         runTime.system(),
         runTime,
-        IOobject::MUST_READ,
+        IOobject::MUST_READ_IF_MODIFIED,
         IOobject::NO_WRITE
     )
 );
diff --git a/src/surfMesh/MeshedSurface/MeshedSurface.C b/src/surfMesh/MeshedSurface/MeshedSurface.C
index 91094607b4..5cc6a1260d 100644
--- a/src/surfMesh/MeshedSurface/MeshedSurface.C
+++ b/src/surfMesh/MeshedSurface/MeshedSurface.C
@@ -374,7 +374,7 @@ Foam::MeshedSurface<Face>::MeshedSurface
             "dummyName",
             t.timeName(),
             t,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         ),
diff --git a/src/surfMesh/surfZone/surfZone/surfZoneIOList.C b/src/surfMesh/surfZone/surfZone/surfZoneIOList.C
index 430b1d2006..c5619801dc 100644
--- a/src/surfMesh/surfZone/surfZone/surfZoneIOList.C
+++ b/src/surfMesh/surfZone/surfZone/surfZoneIOList.C
@@ -45,7 +45,11 @@ Foam::surfZoneIOList::surfZoneIOList
         "(const IOobject& io)";
 
 
-    if (readOpt() == IOobject::MUST_READ)
+    if
+    (
+        readOpt() == IOobject::MUST_READ
+     || readOpt() == IOobject::MUST_READ_IF_MODIFIED
+    )
     {
         surfZoneList& zones = *this;
 
diff --git a/src/surfaceFilmModels/surfaceFilmModel/kinematicSingleLayer/kinematicSingleLayer.C b/src/surfaceFilmModels/surfaceFilmModel/kinematicSingleLayer/kinematicSingleLayer.C
index 090b1091ae..1846f57971 100644
--- a/src/surfaceFilmModels/surfaceFilmModel/kinematicSingleLayer/kinematicSingleLayer.C
+++ b/src/surfaceFilmModels/surfaceFilmModel/kinematicSingleLayer/kinematicSingleLayer.C
@@ -587,7 +587,7 @@ Foam::surfaceFilmModels::kinematicSingleLayer::kinematicSingleLayer
             filmRegionName_,
             time_.timeName(),
             time_,
-            IOobject::MUST_READ
+            IOobject::MUST_READ_IF_MODIFIED
         )
     ),
     nHat_
diff --git a/src/surfaceFilmModels/surfaceFilmModel/surfaceFilmModel/surfaceFilmModel.C b/src/surfaceFilmModels/surfaceFilmModel/surfaceFilmModel/surfaceFilmModel.C
index 6eeb1398fe..5dfb27e1a0 100644
--- a/src/surfaceFilmModels/surfaceFilmModel/surfaceFilmModel/surfaceFilmModel.C
+++ b/src/surfaceFilmModels/surfaceFilmModel/surfaceFilmModel/surfaceFilmModel.C
@@ -74,7 +74,7 @@ Foam::surfaceFilmModels::surfaceFilmModel::surfaceFilmModel
             "surfaceFilmProperties",
             mesh.time().constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
@@ -101,7 +101,7 @@ Foam::surfaceFilmModels::surfaceFilmModel::surfaceFilmModel
             "surfaceFilmProperties",
             mesh.time().constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/surfaceFilmModels/surfaceFilmModel/surfaceFilmModel/surfaceFilmModelNew.C b/src/surfaceFilmModels/surfaceFilmModel/surfaceFilmModel/surfaceFilmModelNew.C
index 78ac50b30f..57347f9132 100644
--- a/src/surfaceFilmModels/surfaceFilmModel/surfaceFilmModel/surfaceFilmModelNew.C
+++ b/src/surfaceFilmModels/surfaceFilmModel/surfaceFilmModel/surfaceFilmModelNew.C
@@ -46,7 +46,7 @@ Foam::surfaceFilmModels::surfaceFilmModel::New
                 "surfaceFilmProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/basic/basicThermo/basicThermo.C b/src/thermophysicalModels/basic/basicThermo/basicThermo.C
index eed0b677d3..91c6be60fc 100644
--- a/src/thermophysicalModels/basic/basicThermo/basicThermo.C
+++ b/src/thermophysicalModels/basic/basicThermo/basicThermo.C
@@ -153,7 +153,7 @@ Foam::basicThermo::basicThermo(const fvMesh& mesh)
             "thermophysicalProperties",
             mesh.time().constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/thermophysicalModels/basic/psiThermo/basicPsiThermo/basicPsiThermoNew.C b/src/thermophysicalModels/basic/psiThermo/basicPsiThermo/basicPsiThermoNew.C
index e6f2d195f0..93b88ad4c4 100644
--- a/src/thermophysicalModels/basic/psiThermo/basicPsiThermo/basicPsiThermoNew.C
+++ b/src/thermophysicalModels/basic/psiThermo/basicPsiThermo/basicPsiThermoNew.C
@@ -43,7 +43,7 @@ Foam::autoPtr<Foam::basicPsiThermo> Foam::basicPsiThermo::New
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/basic/rhoThermo/basicRhoThermo/basicRhoThermoNew.C b/src/thermophysicalModels/basic/rhoThermo/basicRhoThermo/basicRhoThermoNew.C
index b5f8c88073..78423b0234 100644
--- a/src/thermophysicalModels/basic/rhoThermo/basicRhoThermo/basicRhoThermoNew.C
+++ b/src/thermophysicalModels/basic/rhoThermo/basicRhoThermo/basicRhoThermoNew.C
@@ -43,7 +43,7 @@ Foam::autoPtr<Foam::basicRhoThermo> Foam::basicRhoThermo::New
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/chemistryModel/chemistryModel/basicChemistryModel/basicChemistryModel.C b/src/thermophysicalModels/chemistryModel/chemistryModel/basicChemistryModel/basicChemistryModel.C
index 5d8e0285e9..7aa4c2613e 100644
--- a/src/thermophysicalModels/chemistryModel/chemistryModel/basicChemistryModel/basicChemistryModel.C
+++ b/src/thermophysicalModels/chemistryModel/chemistryModel/basicChemistryModel/basicChemistryModel.C
@@ -45,7 +45,7 @@ Foam::basicChemistryModel::basicChemistryModel(const fvMesh& mesh)
             "chemistryProperties",
             mesh.time().constant(),
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/thermophysicalModels/chemistryModel/chemistryModel/psiChemistryModel/psiChemistryModelNew.C b/src/thermophysicalModels/chemistryModel/chemistryModel/psiChemistryModel/psiChemistryModelNew.C
index 38d88071f1..59addc69aa 100644
--- a/src/thermophysicalModels/chemistryModel/chemistryModel/psiChemistryModel/psiChemistryModelNew.C
+++ b/src/thermophysicalModels/chemistryModel/chemistryModel/psiChemistryModel/psiChemistryModelNew.C
@@ -43,7 +43,7 @@ Foam::autoPtr<Foam::psiChemistryModel> Foam::psiChemistryModel::New
                 "chemistryProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/chemistryModel/chemistryModel/rhoChemistryModel/rhoChemistryModelNew.C b/src/thermophysicalModels/chemistryModel/chemistryModel/rhoChemistryModel/rhoChemistryModelNew.C
index 95a6100de5..89439028c9 100644
--- a/src/thermophysicalModels/chemistryModel/chemistryModel/rhoChemistryModel/rhoChemistryModelNew.C
+++ b/src/thermophysicalModels/chemistryModel/chemistryModel/rhoChemistryModel/rhoChemistryModelNew.C
@@ -43,7 +43,7 @@ Foam::autoPtr<Foam::rhoChemistryModel> Foam::rhoChemistryModel::New
                 "chemistryProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/laminarFlameSpeed/laminarFlameSpeed/laminarFlameSpeedNew.C b/src/thermophysicalModels/laminarFlameSpeed/laminarFlameSpeed/laminarFlameSpeedNew.C
index f3e7e6ccc1..ca85cac0da 100644
--- a/src/thermophysicalModels/laminarFlameSpeed/laminarFlameSpeed/laminarFlameSpeedNew.C
+++ b/src/thermophysicalModels/laminarFlameSpeed/laminarFlameSpeed/laminarFlameSpeedNew.C
@@ -40,7 +40,7 @@ Foam::autoPtr<Foam::laminarFlameSpeed> Foam::laminarFlameSpeed::New
             "combustionProperties",
             ct.T().time().constant(),
             ct.T().db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         )
diff --git a/src/thermophysicalModels/radiation/radiationModel/fvDOM/interpolationLookUpTable/interpolationLookUpTable.C b/src/thermophysicalModels/radiation/radiationModel/fvDOM/interpolationLookUpTable/interpolationLookUpTable.C
index 4737759882..90f6c8e54d 100644
--- a/src/thermophysicalModels/radiation/radiationModel/fvDOM/interpolationLookUpTable/interpolationLookUpTable.C
+++ b/src/thermophysicalModels/radiation/radiationModel/fvDOM/interpolationLookUpTable/interpolationLookUpTable.C
@@ -203,7 +203,7 @@ void Foam::interpolationLookUpTable<Type>::readTable
             fileName_,
             instance,
             mesh,
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     );
diff --git a/src/thermophysicalModels/radiation/radiationModel/radiationModel/radiationModel.C b/src/thermophysicalModels/radiation/radiationModel/radiationModel/radiationModel.C
index fd17fe5fd9..d82e1ffe3e 100644
--- a/src/thermophysicalModels/radiation/radiationModel/radiationModel/radiationModel.C
+++ b/src/thermophysicalModels/radiation/radiationModel/radiationModel/radiationModel.C
@@ -51,7 +51,7 @@ Foam::radiation::radiationModel::radiationModel(const volScalarField& T)
             "radiationProperties",
             T.time().constant(),
             T.mesh(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
@@ -79,7 +79,7 @@ Foam::radiation::radiationModel::radiationModel
             "radiationProperties",
             T.time().constant(),
             T.mesh(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/thermophysicalModels/radiation/radiationModel/radiationModel/radiationModelNew.C b/src/thermophysicalModels/radiation/radiationModel/radiationModel/radiationModelNew.C
index 1437b9195d..861708ebec 100644
--- a/src/thermophysicalModels/radiation/radiationModel/radiationModel/radiationModelNew.C
+++ b/src/thermophysicalModels/radiation/radiationModel/radiationModel/radiationModelNew.C
@@ -44,7 +44,7 @@ Foam::radiation::radiationModel::New
                 "radiationProperties",
                 T.time().constant(),
                 T.mesh(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/reactionThermo/combustionThermo/hCombustionThermo/hCombustionThermoNew.C b/src/thermophysicalModels/reactionThermo/combustionThermo/hCombustionThermo/hCombustionThermoNew.C
index 7065df6d07..aa1d03316d 100644
--- a/src/thermophysicalModels/reactionThermo/combustionThermo/hCombustionThermo/hCombustionThermoNew.C
+++ b/src/thermophysicalModels/reactionThermo/combustionThermo/hCombustionThermo/hCombustionThermoNew.C
@@ -44,7 +44,7 @@ Foam::autoPtr<Foam::hCombustionThermo> Foam::hCombustionThermo::New
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
@@ -87,7 +87,7 @@ Foam::autoPtr<Foam::hCombustionThermo> Foam::hCombustionThermo::NewType
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/reactionThermo/combustionThermo/hhuCombustionThermo/hhuCombustionThermoNew.C b/src/thermophysicalModels/reactionThermo/combustionThermo/hhuCombustionThermo/hhuCombustionThermoNew.C
index 5fb31430e7..20117977aa 100644
--- a/src/thermophysicalModels/reactionThermo/combustionThermo/hhuCombustionThermo/hhuCombustionThermoNew.C
+++ b/src/thermophysicalModels/reactionThermo/combustionThermo/hhuCombustionThermo/hhuCombustionThermoNew.C
@@ -44,7 +44,7 @@ Foam::autoPtr<Foam::hhuCombustionThermo> Foam::hhuCombustionThermo::New
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/reactionThermo/combustionThermo/hsCombustionThermo/hsCombustionThermoNew.C b/src/thermophysicalModels/reactionThermo/combustionThermo/hsCombustionThermo/hsCombustionThermoNew.C
index 4e4aecb6c7..9edb9111c2 100644
--- a/src/thermophysicalModels/reactionThermo/combustionThermo/hsCombustionThermo/hsCombustionThermoNew.C
+++ b/src/thermophysicalModels/reactionThermo/combustionThermo/hsCombustionThermo/hsCombustionThermoNew.C
@@ -44,7 +44,7 @@ Foam::autoPtr<Foam::hsCombustionThermo> Foam::hsCombustionThermo::New
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
@@ -87,7 +87,7 @@ Foam::autoPtr<Foam::hsCombustionThermo> Foam::hsCombustionThermo::NewType
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/reactionThermo/reactionThermo/hReactionThermo/hReactionThermoNew.C b/src/thermophysicalModels/reactionThermo/reactionThermo/hReactionThermo/hReactionThermoNew.C
index 3a186ec5ee..df17d001f0 100644
--- a/src/thermophysicalModels/reactionThermo/reactionThermo/hReactionThermo/hReactionThermoNew.C
+++ b/src/thermophysicalModels/reactionThermo/reactionThermo/hReactionThermo/hReactionThermoNew.C
@@ -44,7 +44,7 @@ Foam::autoPtr<Foam::hReactionThermo> Foam::hReactionThermo::New
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
@@ -87,7 +87,7 @@ Foam::autoPtr<Foam::hReactionThermo> Foam::hReactionThermo::NewType
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/thermophysicalModels/reactionThermo/reactionThermo/hsReactionThermo/hsReactionThermoNew.C b/src/thermophysicalModels/reactionThermo/reactionThermo/hsReactionThermo/hsReactionThermoNew.C
index 3607d3458b..0520bb7289 100644
--- a/src/thermophysicalModels/reactionThermo/reactionThermo/hsReactionThermo/hsReactionThermoNew.C
+++ b/src/thermophysicalModels/reactionThermo/reactionThermo/hsReactionThermo/hsReactionThermoNew.C
@@ -44,7 +44,7 @@ Foam::autoPtr<Foam::hsReactionThermo> Foam::hsReactionThermo::New
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
@@ -87,7 +87,7 @@ Foam::autoPtr<Foam::hsReactionThermo> Foam::hsReactionThermo::NewType
                 "thermophysicalProperties",
                 mesh.time().constant(),
                 mesh,
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/topoChangerFvMesh/linearValveFvMesh/linearValveFvMesh.C b/src/topoChangerFvMesh/linearValveFvMesh/linearValveFvMesh.C
index 44d22a1115..88ce5782ad 100644
--- a/src/topoChangerFvMesh/linearValveFvMesh/linearValveFvMesh.C
+++ b/src/topoChangerFvMesh/linearValveFvMesh/linearValveFvMesh.C
@@ -272,8 +272,9 @@ Foam::linearValveFvMesh::linearValveFvMesh(const IOobject& io)
                 "dynamicMeshDict",
                 time().constant(),
                 *this,
-                IOobject::MUST_READ,
-                IOobject::NO_WRITE
+                IOobject::MUST_READ_IF_MODIFIED,
+                IOobject::NO_WRITE,
+                false
             )
         ).subDict(typeName + "Coeffs")
     ),
diff --git a/src/topoChangerFvMesh/linearValveLayersFvMesh/linearValveLayersFvMesh.C b/src/topoChangerFvMesh/linearValveLayersFvMesh/linearValveLayersFvMesh.C
index 636e440b31..f82895bf3b 100644
--- a/src/topoChangerFvMesh/linearValveLayersFvMesh/linearValveLayersFvMesh.C
+++ b/src/topoChangerFvMesh/linearValveLayersFvMesh/linearValveLayersFvMesh.C
@@ -347,8 +347,9 @@ Foam::linearValveLayersFvMesh::linearValveLayersFvMesh(const IOobject& io)
                 "dynamicMeshDict",
                 time().constant(),
                 *this,
-                IOobject::MUST_READ,
-                IOobject::NO_WRITE
+                IOobject::MUST_READ_IF_MODIFIED,
+                IOobject::NO_WRITE,
+                false
             )
         ).subDict(typeName + "Coeffs")
     )
diff --git a/src/topoChangerFvMesh/mixerFvMesh/mixerFvMesh.C b/src/topoChangerFvMesh/mixerFvMesh/mixerFvMesh.C
index 6a050e1c70..e4049f988a 100644
--- a/src/topoChangerFvMesh/mixerFvMesh/mixerFvMesh.C
+++ b/src/topoChangerFvMesh/mixerFvMesh/mixerFvMesh.C
@@ -289,8 +289,9 @@ Foam::mixerFvMesh::mixerFvMesh
                 "dynamicMeshDict",
                 time().constant(),
                 *this,
-                IOobject::MUST_READ,
-                IOobject::NO_WRITE
+                IOobject::MUST_READ_IF_MODIFIED,
+                IOobject::NO_WRITE,
+                false
             )
         ).subDict(typeName + "Coeffs")
     ),
diff --git a/src/topoChangerFvMesh/movingConeTopoFvMesh/movingConeTopoFvMesh.C b/src/topoChangerFvMesh/movingConeTopoFvMesh/movingConeTopoFvMesh.C
index 7de4dcce20..b319e1807a 100644
--- a/src/topoChangerFvMesh/movingConeTopoFvMesh/movingConeTopoFvMesh.C
+++ b/src/topoChangerFvMesh/movingConeTopoFvMesh/movingConeTopoFvMesh.C
@@ -257,8 +257,9 @@ Foam::movingConeTopoFvMesh::movingConeTopoFvMesh(const IOobject& io)
                 "dynamicMeshDict",
                 time().constant(),
                 *this,
-                IOobject::MUST_READ,
-                IOobject::NO_WRITE
+                IOobject::MUST_READ_IF_MODIFIED,
+                IOobject::NO_WRITE,
+                false
             )
         ).subDict(typeName + "Coeffs")
     ),
diff --git a/src/transportModels/incompressible/transportModel/transportModel.C b/src/transportModels/incompressible/transportModel/transportModel.C
index c9a0c8e20d..e45e8206a9 100644
--- a/src/transportModels/incompressible/transportModel/transportModel.C
+++ b/src/transportModels/incompressible/transportModel/transportModel.C
@@ -43,7 +43,7 @@ Foam::transportModel::transportModel
             "transportProperties",
             U.time().constant(),
             U.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     )
diff --git a/src/triSurface/triSurface/surfacePatch/surfacePatchIOList.C b/src/triSurface/triSurface/surfacePatch/surfacePatchIOList.C
index dc044c2d17..849ab59c14 100644
--- a/src/triSurface/triSurface/surfacePatch/surfacePatchIOList.C
+++ b/src/triSurface/triSurface/surfacePatch/surfacePatchIOList.C
@@ -46,8 +46,26 @@ Foam::surfacePatchIOList::surfacePatchIOList
         "(const IOobject& io)";
 
 
-    if (readOpt() == IOobject::MUST_READ)
+    if
+    (
+        readOpt() == IOobject::MUST_READ
+     || readOpt() == IOobject::MUST_READ_IF_MODIFIED
+    )
     {
+        if (readOpt() == IOobject::MUST_READ_IF_MODIFIED)
+        {
+            WarningIn
+            (
+                "surfacePatchIOList::surfacePatchIOList\n"
+                "(\n"
+                "    const IOobject&\n"
+                ")"
+            )   << "Specified IOobject::MUST_READ_IF_MODIFIED but class"
+                << " does not support automatic rereading."
+                << endl;
+        }
+
+
         surfacePatchList& patches = *this;
 
         // read polyPatchList
diff --git a/src/turbulenceModels/compressible/LES/LESModel/LESModel.C b/src/turbulenceModels/compressible/LES/LESModel/LESModel.C
index e95f9def5c..bf1f726c32 100644
--- a/src/turbulenceModels/compressible/LES/LESModel/LESModel.C
+++ b/src/turbulenceModels/compressible/LES/LESModel/LESModel.C
@@ -70,7 +70,7 @@ LESModel::LESModel
             "LESProperties",
             U.time().constant(),
             U.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
@@ -111,7 +111,7 @@ autoPtr<LESModel> LESModel::New
                 "LESProperties",
                 U.time().constant(),
                 U.db(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/turbulenceModels/compressible/RAS/RASModel/RASModel.C b/src/turbulenceModels/compressible/RAS/RASModel/RASModel.C
index 755318a1d8..64594ff010 100644
--- a/src/turbulenceModels/compressible/RAS/RASModel/RASModel.C
+++ b/src/turbulenceModels/compressible/RAS/RASModel/RASModel.C
@@ -71,7 +71,7 @@ RASModel::RASModel
             "RASProperties",
             U.time().constant(),
             U.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
@@ -117,7 +117,7 @@ autoPtr<RASModel> RASModel::New
                 "RASProperties",
                 U.time().constant(),
                 U.db(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/turbulenceModels/compressible/RAS/derivedFvPatchFields/turbulentTemperatureCoupledBaffle/regionProperties.C b/src/turbulenceModels/compressible/RAS/derivedFvPatchFields/turbulentTemperatureCoupledBaffle/regionProperties.C
index 89eaaabd48..f85e8f5440 100644
--- a/src/turbulenceModels/compressible/RAS/derivedFvPatchFields/turbulentTemperatureCoupledBaffle/regionProperties.C
+++ b/src/turbulenceModels/compressible/RAS/derivedFvPatchFields/turbulentTemperatureCoupledBaffle/regionProperties.C
@@ -36,7 +36,7 @@ Foam::regionProperties::regionProperties(const Time& runTime)
             "regionProperties",
             runTime.time().constant(),
             runTime.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
diff --git a/src/turbulenceModels/compressible/turbulenceModel/turbulenceModel.C b/src/turbulenceModels/compressible/turbulenceModel/turbulenceModel.C
index 19f31068bf..da27aa55ec 100644
--- a/src/turbulenceModels/compressible/turbulenceModel/turbulenceModel.C
+++ b/src/turbulenceModels/compressible/turbulenceModel/turbulenceModel.C
@@ -81,7 +81,7 @@ autoPtr<turbulenceModel> turbulenceModel::New
                 "turbulenceProperties",
                 U.time().constant(),
                 U.db(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/turbulenceModels/incompressible/LES/LESModel/LESModel.C b/src/turbulenceModels/incompressible/LES/LESModel/LESModel.C
index 574e387f1c..1246bdc801 100644
--- a/src/turbulenceModels/incompressible/LES/LESModel/LESModel.C
+++ b/src/turbulenceModels/incompressible/LES/LESModel/LESModel.C
@@ -69,7 +69,7 @@ LESModel::LESModel
             "LESProperties",
             U.time().constant(),
             U.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
@@ -108,7 +108,7 @@ autoPtr<LESModel> LESModel::New
                 "LESProperties",
                 U.time().constant(),
                 U.db(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/turbulenceModels/incompressible/RAS/RASModel/RASModel.C b/src/turbulenceModels/incompressible/RAS/RASModel/RASModel.C
index 87d50dedd7..27e465720f 100644
--- a/src/turbulenceModels/incompressible/RAS/RASModel/RASModel.C
+++ b/src/turbulenceModels/incompressible/RAS/RASModel/RASModel.C
@@ -70,7 +70,7 @@ RASModel::RASModel
             "RASProperties",
             U.time().constant(),
             U.db(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE
         )
     ),
@@ -115,7 +115,7 @@ autoPtr<RASModel> RASModel::New
                 "RASProperties",
                 U.time().constant(),
                 U.db(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )
diff --git a/src/turbulenceModels/incompressible/RAS/derivedFvPatchFields/wallFunctions/nutWallFunctions/nutUTabulatedWallFunction/nutUTabulatedWallFunctionFvPatchScalarField.C b/src/turbulenceModels/incompressible/RAS/derivedFvPatchFields/wallFunctions/nutWallFunctions/nutUTabulatedWallFunction/nutUTabulatedWallFunctionFvPatchScalarField.C
index 79e9ab8383..d211671ff4 100644
--- a/src/turbulenceModels/incompressible/RAS/derivedFvPatchFields/wallFunctions/nutWallFunctions/nutUTabulatedWallFunction/nutUTabulatedWallFunctionFvPatchScalarField.C
+++ b/src/turbulenceModels/incompressible/RAS/derivedFvPatchFields/wallFunctions/nutWallFunctions/nutUTabulatedWallFunction/nutUTabulatedWallFunctionFvPatchScalarField.C
@@ -138,7 +138,7 @@ nutUTabulatedWallFunctionFvPatchScalarField
             uPlusTableName_,
             patch().boundaryMesh().mesh().time().constant(),
             patch().boundaryMesh().mesh(),
-            IOobject::MUST_READ,
+            IOobject::MUST_READ_IF_MODIFIED,
             IOobject::NO_WRITE,
             false
         ),
diff --git a/src/turbulenceModels/incompressible/turbulenceModel/turbulenceModel.C b/src/turbulenceModels/incompressible/turbulenceModel/turbulenceModel.C
index 1aeea66fd3..79e94c0741 100644
--- a/src/turbulenceModels/incompressible/turbulenceModel/turbulenceModel.C
+++ b/src/turbulenceModels/incompressible/turbulenceModel/turbulenceModel.C
@@ -77,7 +77,7 @@ autoPtr<turbulenceModel> turbulenceModel::New
                 "turbulenceProperties",
                 U.time().constant(),
                 U.db(),
-                IOobject::MUST_READ,
+                IOobject::MUST_READ_IF_MODIFIED,
                 IOobject::NO_WRITE,
                 false
             )