diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
index eb7032a593..91a4f68534 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
@@ -96,11 +96,7 @@ void Foam::masterOFstream::commit()
         filePaths[Pstream::myProcNo()] = pathName_;
         Pstream::gatherList(filePaths);
 
-        bool uniform =
-            fileOperations::masterUncollatedFileOperation::uniformFile
-            (
-                filePaths
-            );
+        bool uniform = fileOperation::uniformFile(filePaths);
 
         Pstream::broadcast(uniform);
 
diff --git a/src/OpenFOAM/global/argList/argList.C b/src/OpenFOAM/global/argList/argList.C
index a2e79e3fc5..c5a52d07ee 100644
--- a/src/OpenFOAM/global/argList/argList.C
+++ b/src/OpenFOAM/global/argList/argList.C
@@ -1815,7 +1815,7 @@ Foam::argList::~argList()
     jobInfo.stop();     // Normal job termination
 
     // Delete file handler to flush any remaining IO
-    Foam::fileHandler(nullptr);
+    (void)Foam::fileHandler(nullptr);
 }
 
 
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
index a8430c56a8..ec67865fca 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
@@ -287,7 +287,7 @@ Foam::fileOperations::collatedFileOperation::collatedFileOperation
         ),
         false
     ),
-    myComm_(comm_),
+    managedComm_(comm_),
     writer_(mag(maxThreadFileBufferSize), comm_),
     nProcs_(Pstream::nProcs()),
     ioRanks_(ioRanks())
@@ -305,7 +305,7 @@ Foam::fileOperations::collatedFileOperation::collatedFileOperation
 )
 :
     masterUncollatedFileOperation(comm, false),
-    myComm_(-1),
+    managedComm_(-1),  // Externally managed
     writer_(mag(maxThreadFileBufferSize), comm),
     nProcs_(Pstream::nProcs()),
     ioRanks_(ioRanks)
@@ -321,9 +321,9 @@ Foam::fileOperations::collatedFileOperation::~collatedFileOperation()
     // Wait for any outstanding file operations
     flush();
 
-    if (myComm_ != -1 && myComm_ != UPstream::worldComm)
+    if (UPstream::isUserComm(managedComm_))
     {
-        UPstream::freeCommunicator(myComm_);
+        UPstream::freeCommunicator(managedComm_);
     }
 }
 
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.H b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.H
index efdbbb1abc..b789fee4a9 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.H
@@ -67,6 +67,12 @@ class collatedFileOperation
 :
     public masterUncollatedFileOperation
 {
+    // Private Data
+
+        //- Communicator allocated/managed by us
+        label managedComm_;
+
+
     // Private Member Functions
 
         //- Any initialisation steps after constructing
@@ -76,9 +82,6 @@ protected:
 
     // Protected Data
 
-        //- Any communicator allocated by me
-        const label myComm_;
-
         //- Threaded writer
         mutable OFstreamCollator writer_;
 
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.C
index 73fcd410fd..f86e2c6ca3 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.C
@@ -149,7 +149,8 @@ Foam::fileOperations::hostCollatedFileOperation::hostCollatedFileOperation
         (Pstream::parRun() ? labelList() : ioRanks()), // processor dirs
         typeName,
         false // verbose
-    )
+    ),
+    managedComm_(comm_)
 {
     init(verbose);
 }
@@ -159,9 +160,9 @@ Foam::fileOperations::hostCollatedFileOperation::hostCollatedFileOperation
 
 Foam::fileOperations::hostCollatedFileOperation::~hostCollatedFileOperation()
 {
-    if (comm_ != -1 && comm_ != UPstream::worldComm)
+    if (UPstream::isUserComm(managedComm_))
     {
-        UPstream::freeCommunicator(comm_);
+        UPstream::freeCommunicator(managedComm_);
     }
 }
 
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.H b/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.H
index 0f8e0fafbf..859d2705a1 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017-2018 OpenFOAM Foundation
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -77,6 +77,12 @@ class hostCollatedFileOperation
 :
     public collatedFileOperation
 {
+    // Private Data
+
+        //- Communicator allocated/managed by us
+        label managedComm_;
+
+
     // Private Member Functions
 
         //- Any initialisation steps after constructing
diff --git a/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.C b/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.C
index b2fae3dc7d..9816c4fe56 100644
--- a/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.C
@@ -295,6 +295,42 @@ Foam::fileOperation::sortTimes
 }
 
 
+bool Foam::fileOperation::uniformFile(const fileNameList& names)
+{
+    if (names.empty())
+    {
+        return false;
+    }
+
+    const auto& object0 = names[0];
+
+    for (label i = 1; i < names.size(); ++i)
+    {
+        if (object0 != names[i])
+        {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+
+bool Foam::fileOperation::uniformFile(const label comm, const fileName& name)
+{
+    if (!Pstream::parRun())
+    {
+        return true;
+    }
+
+    fileName masterName(name);
+
+    Pstream::broadcast(masterName, comm);
+
+    return returnReduceAnd((masterName == name), comm);
+}
+
+
 // * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //
 
 Foam::fileMonitor& Foam::fileOperation::monitor() const
@@ -710,6 +746,18 @@ Foam::fileOperation::New
     bool verbose
 )
 {
+    if (handlerType.empty())
+    {
+        if (fileOperation::defaultFileHandler.empty())
+        {
+            FatalErrorInFunction
+                << "defaultFileHandler name is undefined" << nl
+                << abort(FatalError);
+        }
+
+        return fileOperation::New(fileOperation::defaultFileHandler, verbose);
+    }
+
     DebugInFunction
         << "Constructing fileHandler" << endl;
 
@@ -1511,37 +1559,56 @@ const Foam::fileOperation& Foam::fileHandler()
 {
     if (!fileOperation::fileHandlerPtr_)
     {
-        word handler(Foam::getEnv("FOAM_FILEHANDLER"));
+        word handlerType(Foam::getEnv("FOAM_FILEHANDLER"));
 
-        if (handler.empty())
+        if (handlerType.empty())
         {
-            handler = fileOperation::defaultFileHandler;
+            handlerType = fileOperation::defaultFileHandler;
         }
 
-        fileOperation::fileHandlerPtr_ = fileOperation::New(handler, true);
+        fileOperation::fileHandlerPtr_ = fileOperation::New(handlerType, true);
     }
 
     return *fileOperation::fileHandlerPtr_;
 }
 
 
+Foam::autoPtr<Foam::fileOperation>
+Foam::fileHandler(std::nullptr_t)
+{
+    return autoPtr<fileOperation>(fileOperation::fileHandlerPtr_.release());
+}
+
+
 Foam::autoPtr<Foam::fileOperation>
 Foam::fileHandler(autoPtr<fileOperation>&& newHandler)
 {
+    // - do nothing if newHandler is empty. Does not delete current
+    // - do nothing if newHandler is identical to current handler
+
+    // Change ownership as atomic operations
+
+    // If newHandler and current handler are actually identical, we
+    // have a bit problem somewhere else since this means that the pointer
+    // is managed is done in two places!
+    // Should flag as a FatalError (in the future), but there may still be
+    // some place where we would like to fake shared pointers?
+
+    // TBD: add a flush() operation on the old handler first,
+    // instead of waiting for it to be run on destruction?
+
+    autoPtr<fileOperation> old;
+
     if
     (
-        newHandler
-     && fileOperation::fileHandlerPtr_
-     && newHandler->type() == fileOperation::fileHandlerPtr_->type()
+        newHandler.get() != nullptr
+     && newHandler.get() != fileOperation::fileHandlerPtr_.get()
     )
     {
-        return nullptr;  // No change
+        old.reset(newHandler.release());
+        old.swap(fileOperation::fileHandlerPtr_);
     }
 
-    autoPtr<fileOperation> old(std::move(fileOperation::fileHandlerPtr_));
-
-    fileOperation::fileHandlerPtr_ = std::move(newHandler);
-
     return old;
 }
 
diff --git a/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.H b/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.H
index 956a68a48a..982ac5dfe4 100644
--- a/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.H
@@ -196,6 +196,9 @@ public:
             const bool distributedRoots = false
         );
 
+        //- Clone fileHandler
+        /// virtual autoPtr<fileOperation> clone() const = 0;
+
 
     // Declare run-time constructor selection table
 
@@ -213,7 +216,8 @@ public:
 
     // Selectors
 
-        //- Select fileHandler-type
+        //- Select fileHandler-type.
+        //- Uses defaultFileHandler if the handlerType is empty.
         static autoPtr<fileOperation> New
         (
             const word& handlerType,
@@ -235,6 +239,12 @@ public:
             const word& constantName = "constant"
         );
 
+        //- True if the file names are identical. False on an empty list
+        static bool uniformFile(const fileNameList& names);
+
+        //- True if the file name is identical on all ranks
+        static bool uniformFile(const label comm, const fileName& name);
+
 
     // Member Functions
 
@@ -628,11 +638,21 @@ inline Ostream& operator<<(Ostream& os, const fileOperation::pathType b)
 
 // Note: defined in fileOperation.C
 
-//- Get current file handler
+//- Return the current file handler.
+//- Will create the default file handler if necessary.
 const fileOperation& fileHandler();
 
-//- Replace, reset file handler.
-//  \return old handler on change, null otherwise
+//- Delete current file handler.
+//  \returns the old handler
+autoPtr<fileOperation> fileHandler(std::nullptr_t);
+
+//- Replace the current file handler.
+//  The following are considered no-ops:
+//  - an empty/invalid newHandler does \b not delete,
+//    use fileHandler(std::nullptr_t) - ie, a literal \c nullptr for that
+//  - if new handler and current handler are identical (same pointer).
+//  .
+//  \returns the old handler (on change), nullptr otherwise
 autoPtr<fileOperation> fileHandler(autoPtr<fileOperation>&& newHandler);
 
 
diff --git a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C
index 72d0849c39..a6030560f0 100644
--- a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C
@@ -474,24 +474,6 @@ Foam::fileOperations::masterUncollatedFileOperation::localObjectPath
 }
 
 
-bool Foam::fileOperations::masterUncollatedFileOperation::uniformFile
-(
-    const fileNameList& filePaths
-)
-{
-    const fileName& object0 = filePaths[0];
-
-    for (label i = 1; i < filePaths.size(); i++)
-    {
-        if (filePaths[i] != object0)
-        {
-            return false;
-        }
-    }
-    return true;
-}
-
-
 void Foam::fileOperations::masterUncollatedFileOperation::readAndSend
 (
     const fileName& filePath,
@@ -763,7 +745,7 @@ masterUncollatedFileOperation
             subRanks(Pstream::nProcs())
         )
     ),
-    myComm_(comm_)
+    managedComm_(comm_)
 {
     init(verbose);
 }
@@ -777,7 +759,7 @@ masterUncollatedFileOperation
 )
 :
     fileOperation(comm),
-    myComm_(-1)
+    managedComm_(-1)  // Externally managed
 {
     init(verbose);
 }
@@ -788,9 +770,9 @@ masterUncollatedFileOperation
 Foam::fileOperations::masterUncollatedFileOperation::
 ~masterUncollatedFileOperation()
 {
-    if (myComm_ != -1 && myComm_ != UPstream::worldComm)
+    if (UPstream::isUserComm(managedComm_))
     {
-        UPstream::freeCommunicator(myComm_);
+        UPstream::freeCommunicator(managedComm_);
     }
 }
 
diff --git a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.H b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.H
index 415e572afd..54ce0dbd38 100644
--- a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.H
@@ -88,6 +88,12 @@ class masterUncollatedFileOperation
 :
     public fileOperation
 {
+    // Private Data
+
+        //- Communicator allocated/managed by us
+        label managedComm_;
+
+
     // Private Member Functions
 
         //- Any initialisation steps after constructing
@@ -97,9 +103,6 @@ protected:
 
     // Protected Data
 
-        //- Any communicator allocated by me
-        const label myComm_;
-
         //- Cached times for a given directory
         mutable HashPtrTable<DynamicList<instant>> times_;
 
@@ -744,9 +747,6 @@ public:
 
         // Other
 
-            //- Same file?
-            static bool uniformFile(const fileNameList&);
-
             //- Get sorted list of times
             virtual instantList findTimes(const fileName&, const word&) const;
 
diff --git a/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.C b/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.C
index 340a75c413..39181c4702 100644
--- a/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.C
@@ -193,12 +193,24 @@ Foam::fileOperations::uncollatedFileOperation::uncollatedFileOperation
     bool verbose
 )
 :
-    fileOperation(Pstream::worldComm)
+    fileOperation(UPstream::worldComm),
+    managedComm_(-1)  // worldComm is externally managed
 {
     init(verbose);
 }
 
 
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+Foam::fileOperations::uncollatedFileOperation::~uncollatedFileOperation()
+{
+    if (UPstream::isUserComm(managedComm_))
+    {
+        UPstream::freeCommunicator(managedComm_);
+    }
+}
+
+
 // * * * * * * * * * * * * * Filesystem Operations * * * * * * * * * * * * * //
 
 bool Foam::fileOperations::uncollatedFileOperation::mkDir
diff --git a/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.H b/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.H
index 31e75ddb0d..66949b2adc 100644
--- a/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.H
@@ -53,6 +53,12 @@ class uncollatedFileOperation
 :
     public fileOperation
 {
+    // Private Data
+
+        //- Communicator allocated/managed by us
+        label managedComm_;
+
+
     // Private Member Functions
 
         //- Any initialisation steps after constructing
@@ -95,7 +101,7 @@ public:
 
 
     //- Destructor
-    virtual ~uncollatedFileOperation() = default;
+    virtual ~uncollatedFileOperation();
 
 
     // Member Functions