diff --git a/applications/test/OFstream/Make/files b/applications/test/OFstream/Make/files
new file mode 100644
index 0000000000..7c5032c730
--- /dev/null
+++ b/applications/test/OFstream/Make/files
@@ -0,0 +1,3 @@
+Test-OFstream.C
+
+EXE = $(FOAM_USER_APPBIN)/Test-OFstream
diff --git a/applications/test/OFstream/Make/options b/applications/test/OFstream/Make/options
new file mode 100644
index 0000000000..18e6fe47af
--- /dev/null
+++ b/applications/test/OFstream/Make/options
@@ -0,0 +1,2 @@
+/* EXE_INC = */
+/* EXE_LIBS = */
diff --git a/applications/test/OFstream/Test-OFstream.C b/applications/test/OFstream/Test-OFstream.C
new file mode 100644
index 0000000000..ac108699b0
--- /dev/null
+++ b/applications/test/OFstream/Test-OFstream.C
@@ -0,0 +1,228 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+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/>.
+
+Description
+    Test OFstream. Primarily atomic operations
+
+\*---------------------------------------------------------------------------*/
+
+#include "Fstream.H"
+#include "IOstreams.H"
+#include "OSspecific.H"
+#include "argList.H"
+#include "ListOps.H"
+
+using namespace Foam;
+
+void listFiles(const fileName& dir)
+{
+    wordList files = ListOps::create<word>
+    (
+        readDir(dir, fileName::FILE),
+        nameOp<fileName>()
+    );
+
+    Info
+        << nl
+        << "files:" << nl
+        << files << nl
+        << "ls" << nl
+        << "============" << endl;
+    Foam::system("ls -al " + dir);
+    Info<< "============" << endl;
+}
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+// Main program:
+
+int main(int argc, char *argv[])
+{
+    argList::addBoolOption("gz", "Use compression");
+    argList::addBoolOption("append", "Use append mode");
+    argList::addBoolOption("atomic", "Use atomic");
+    argList::addBoolOption("keep", "Do not remove test directory");
+    argList::addOption("write", "file", "test writing to file");
+
+    #include "setRootCase.H"
+
+    const fileName baseDir("Test-OFstream-directory");
+
+    Foam::mkDir(baseDir);
+
+    InfoErr<< "mkdir: " << baseDir << endl;
+
+    IOstreamOption streamOpt;
+
+    if (args.found("gz"))
+    {
+        streamOpt.compression(IOstreamOption::COMPRESSED);
+    }
+
+    IOstreamOption::appendType append =
+    (
+        args.found("append")
+      ? IOstreamOption::APPEND
+      : IOstreamOption::NON_APPEND
+    );
+    IOstreamOption::atomicType atomic =
+    (
+        args.found("atomic")
+      ? IOstreamOption::ATOMIC
+      : IOstreamOption::NON_ATOMIC
+    );
+
+    {
+        OFstream(baseDir/"dummy")() << "Some file content" << endl;
+
+        Foam::ln("dummy", baseDir/"Test2.txt");
+        Foam::ln("dummy", baseDir/"Test3.txt");
+        Foam::ln("dummy", baseDir/"Test4.txt");
+        Foam::ln("dummy", baseDir/"Test4.txt.gz");
+        Foam::ln("dummy", baseDir/"Test5.txt");
+        Foam::ln("dummy", baseDir/"Test5.txt.gz");
+    }
+
+    {
+        OFstream os
+        (
+            atomic,
+            baseDir/"Test1.txt",
+            streamOpt,
+            append
+        );
+
+        os << "=========================" << endl;
+
+        InfoErr<< "open: " << os.name() << endl;
+        InfoErr<< "... sleep" << endl;
+
+        listFiles(baseDir);
+
+        sleep(2);
+
+        os << "+++++++++++++++++++++++++++++++++++" << endl;
+    }
+
+    {
+        OFstream os
+        (
+            atomic,
+            baseDir/"Test2.txt",
+            streamOpt
+            // NON_APPEND
+        );
+
+        os << "=========================" << endl;
+
+        InfoErr<< "open: " << os.name() << endl;
+        InfoErr<< "... sleep" << endl;
+
+        listFiles(baseDir);
+
+        sleep(2);
+
+        os << "+++++++++++++++++++++++++++++++++++" << endl;
+    }
+    {
+        OFstream os
+        (
+            atomic,
+            baseDir/"Test3.txt",
+            streamOpt,
+            IOstreamOption::APPEND
+        );
+
+        os << "=========================" << endl;
+
+        InfoErr<< "open: " << os.name() << endl;
+        InfoErr<< "... sleep" << endl;
+
+        listFiles(baseDir);
+
+        sleep(2);
+
+        os << "+++++++++++++++++++++++++++++++++++" << endl;
+    }
+    {
+        OFstream os
+        (
+            baseDir/"Test4.txt",
+            IOstreamOption::ASCII,
+            IOstreamOption::COMPRESSED
+        );
+
+        os << "=========================" << endl;
+
+        InfoErr<< "open: " << os.name() << endl;
+        InfoErr<< "... sleep" << endl;
+
+        listFiles(baseDir);
+
+        sleep(2);
+
+        os << "+++++++++++++++++++++++++++++++++++" << endl;
+    }
+    {
+        OFstream os
+        (
+            IOstreamOption::ATOMIC,
+            baseDir/"Test5.txt"
+            // ASCII UNCOMPRESSED NON_APPEND
+        );
+
+        os << "=========================" << endl;
+
+        InfoErr<< "open: " << os.name() << endl;
+        InfoErr<< "... sleep" << endl;
+
+        listFiles(baseDir);
+
+        sleep(2);
+
+        os << "+++++++++++++++++++++++++++++++++++" << endl;
+    }
+
+    Info<< nl << "done:" << endl;
+
+    listFiles(baseDir);
+
+    if (args.found("keep"))
+    {
+        InfoErr<< "keep: " << baseDir << endl;
+    }
+    else
+    {
+        InfoErr<< "rmdir: " << baseDir << endl;
+        Foam::rmDir(baseDir);
+    }
+
+    Info<< "\nEnd\n" << endl;
+
+    return 0;
+}
+
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.C b/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.C
index 8829cbc877..e59bad6f8f 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.C
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.C
@@ -126,7 +126,7 @@ void Foam::IFstream::rewind()
     if (IOstreamOption::COMPRESSED == ifstreamPointer::whichCompression())
     {
         lineNumber_ = 1;  // Reset line number
-        ifstreamPointer::reopen_gz(this->name() + ".gz");
+        ifstreamPointer::reopen_gz(this->name());
         setState(ifstreamPointer::get()->rdstate());
     }
     else
@@ -150,7 +150,7 @@ Foam::IFstream& Foam::IFstream::operator()() const
     if (!good())
     {
         // Also checks .gz file
-        if (isFile(this->name(), true))
+        if (Foam::isFile(this->name(), true))
         {
             check(FUNCTION_NAME);
             FatalIOError.exit();
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.H b/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.H
index 989ebaf77e..f178fd95cc 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.H
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.H
@@ -64,14 +64,14 @@ public:
 
     // Constructors
 
-        //- Construct from pathname
+        //- Construct from pathname, default or specified stream options
         explicit IFstream
         (
             const fileName& pathname,
             IOstreamOption streamOpt = IOstreamOption()
         );
 
-        //- Construct from pathname, format (version)
+        //- Construct from pathname and format
         IFstream
         (
             const fileName& pathname,
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.C b/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.C
index 880651ba8f..fc65cfd462 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.C
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.C
@@ -56,12 +56,19 @@ Foam::OFstream::OFstream
 
 Foam::OFstream::OFstream
 (
+    IOstreamOption::atomicType atomic,
     const fileName& pathname,
     IOstreamOption streamOpt,
-    const bool append
+    IOstreamOption::appendType append
 )
 :
-    Foam::ofstreamPointer(pathname, streamOpt.compression(), append),
+    Foam::ofstreamPointer
+    (
+        pathname,
+        streamOpt.compression(),
+        (IOstreamOption::appendType::APPEND == append),
+        (IOstreamOption::atomicType::ATOMIC == atomic)
+    ),
     OSstream(*(ofstreamPointer::get()), pathname, streamOpt)
 {
     setClosed();
@@ -100,7 +107,9 @@ Foam::OFstream::OFstream
 // * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
 
 Foam::OFstream::~OFstream()
-{}
+{
+    ofstreamPointer::close(this->name());
+}
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
@@ -137,15 +146,8 @@ const std::ostream& Foam::OFstream::stdStream() const
 
 void Foam::OFstream::rewind()
 {
-    if (IOstreamOption::COMPRESSED == ofstreamPointer::whichCompression())
-    {
-        ofstreamPointer::reopen_gz(this->name() + ".gz");
-    }
-    else
-    {
-        // Reopen (truncate)
-        ofstreamPointer::reopen(this->name());
-    }
+    // Reopen (truncate) std::ostream
+    ofstreamPointer::reopen(this->name());
 
     // As per OSstream::rewind()
 
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.H b/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.H
index 674fc97cd5..488c878471 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.H
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.H
@@ -68,28 +68,57 @@ public:
         //  Behaves like \c /dev/null and is named accordingly
         explicit OFstream(std::nullptr_t);
 
-        //- Construct from pathname
+        //- Construct with specified atomic behaviour
+        //- from pathname, stream option, optional append
+        OFstream
+        (
+            IOstreamOption::atomicType atomic,
+            const fileName& pathname,
+            IOstreamOption streamOpt = IOstreamOption(),
+            IOstreamOption::appendType append = IOstreamOption::NON_APPEND
+        );
+
+        //- Construct from pathname and other specifications
         explicit OFstream
         (
             const fileName& pathname,
             IOstreamOption streamOpt = IOstreamOption(),
-            const bool append = false
-        );
+            IOstreamOption::appendType append = IOstreamOption::NON_APPEND
+        )
+        :
+            OFstream(IOstreamOption::NON_ATOMIC, pathname, streamOpt, append)
+        {}
 
-        //- Construct from pathname, format (uncompressed), optional append
+        //- Construct from pathname, format (uncompressed), optional append,
+        //- atomic behaviour as per system default
         OFstream
         (
             const fileName& pathname,
             IOstreamOption::streamFormat fmt,
             IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED,
-            const bool append = false
+            IOstreamOption::appendType append = IOstreamOption::NON_APPEND
         )
         :
             OFstream(pathname, IOstreamOption(fmt, cmp), append)
         {}
 
+        //- Construct with specified atomic behaviour
+        //- from pathname, format (uncompressed), optional append
+        OFstream
+        (
+            IOstreamOption::atomicType atomic,
+            const fileName& pathname,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED,
+            IOstreamOption::appendType append = IOstreamOption::NON_APPEND
+        )
+        :
+            OFstream(atomic, pathname, IOstreamOption(fmt, cmp), append)
+        {}
 
-    //- Destructor
+
+    //- Destructor. Possibly invokes an atomic rename
+    //- (preference defined during construction)
     ~OFstream();
 
 
@@ -122,13 +151,14 @@ public:
     #ifdef Foam_IOstream_extras
 
         //- Construct from pathname, format (version, compression)
+        FOAM_DEPRECATED_FOR(2022-09, "Construct without specifying version")
         OFstream
         (
             const fileName& pathname,
             IOstreamOption::streamFormat fmt,
             IOstreamOption::versionNumber ver,
             IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED,
-            const bool append = false
+            IOstreamOption::appendType append = IOstreamOption::NON_APPEND
         )
         :
             OFstream(pathname, IOstreamOption(fmt, ver, cmp), append)
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/fstreamPointer.H b/src/OpenFOAM/db/IOstreams/Fstreams/fstreamPointer.H
index 6fb70c0b0a..4fb72dbd3e 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/fstreamPointer.H
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/fstreamPointer.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -77,12 +77,14 @@ class ifstreamPointer
         //- The stream pointer (ifstream or igzstream)
         std::unique_ptr<std::istream> ptr_;
 
+
 protected:
 
     // Protected Member Functions
 
         //- Special 'rewind' method for compressed stream
-        void reopen_gz(const std::string& pathname_gz);
+        void reopen_gz(const std::string& pathname);
+
 
 public:
 
@@ -109,7 +111,9 @@ public:
 
     // Constructors
 
-        //- Construct from pathname
+        //- Construct from pathname.
+        //  Attempts to read the specified file.
+        //  If that fails, try as a compressed file (.gz ending).
         explicit ifstreamPointer(const fileName& pathname);
 
 
@@ -167,23 +171,25 @@ class ofstreamPointer
         //- The stream pointer (ofstream | ogzstream | ocountstream)
         std::unique_ptr<std::ostream> ptr_;
 
+        //- Atomic file creation
+        bool atomic_;
+
+
 protected:
 
     // Protected Member Functions
 
-        //- Special 'rewind' method for compressed stream
-        void reopen_gz(const std::string& pathname_gz);
-
-        //- General 'rewind' method (non-compressed)
+        //- Reopen for compressed/non-compressed
         void reopen(const std::string& pathname);
 
+        //- Close stream and rename file
+        void close(const std::string& pathname);
+
+
 public:
 
     // Generated Methods
 
-        //- Default construct (empty)
-        ofstreamPointer() noexcept = default;
-
         //- No copy construct
         ofstreamPointer(const ofstreamPointer&) = delete;
 
@@ -202,22 +208,25 @@ public:
 
     // Constructors
 
+        //- Default construct (empty)
+        ofstreamPointer() noexcept;
+
         //- Construct as null output stream using Foam::ocountstream
         explicit ofstreamPointer(std::nullptr_t);
 
-        //- Construct from pathname, with specified append option
-        ofstreamPointer(const fileName& pathname, const bool append)
-        :
-            ofstreamPointer(pathname, IOstreamOption::UNCOMPRESSED, append)
-        {}
-
-        //- Construct from pathname,
-        //- with preferred compression and specified append option
+        //- Construct from pathname, compression, append, file handling atomic
+        //  \param pathname The file name to open for writing
+        //  \param comp     UNCOMPRESSED | COMPRESSED
+        //  \param append   Open in append mode
+        //  \param atomic   Write into temporary file (not target file).
+        //      This option should only be used with a stream wrapper
+        //      (eg, OFstream) that handles the final renaming.
         explicit ofstreamPointer
         (
             const fileName& pathname,
             IOstreamOption::compressionType comp = IOstreamOption::UNCOMPRESSED,
-            const bool append = false
+            const bool append = false,
+            const bool atomic = false
         );
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/fstreamPointers.C b/src/OpenFOAM/db/IOstreams/Fstreams/fstreamPointers.C
index 612f97ca3a..16815f7a0a 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/fstreamPointers.C
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/fstreamPointers.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011 OpenFOAM Foundation
-    Copyright (C) 2018-2021 OpenCFD Ltd.
+    Copyright (C) 2018-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -29,6 +29,7 @@ License
 #include "fstreamPointer.H"
 #include "OCountStream.H"
 #include "OSspecific.H"
+#include <cstdio>
 
 // HAVE_LIBZ defined externally
 // #define HAVE_LIBZ
@@ -37,37 +38,6 @@ License
 #include "gzstream.h"
 #endif /* HAVE_LIBZ */
 
-// * * * * * * * * * * * * * * * Local Functions * * * * * * * * * * * * * * //
-
-namespace Foam
-{
-    static inline void removeConflictingFiles
-    (
-        const fileName& otherName,
-        const bool append,
-        const fileName& targetName
-    )
-    {
-        // Remove other (compressed/uncompressed) version
-
-        const fileName::Type pathType = Foam::type(otherName, false);
-
-        if (pathType == fileName::FILE || pathType == fileName::SYMLINK)
-        {
-            Foam::rm(otherName);
-        }
-
-        // Disallow writing into symlinked files.
-        // Eg, avoid problems with symlinked initial fields
-
-        if (!append && Foam::type(targetName, false) == fileName::SYMLINK)
-        {
-            Foam::rm(targetName);
-        }
-    }
-}
-
-
 // * * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * //
 
 bool Foam::ifstreamPointer::supports_gz()
@@ -112,7 +82,7 @@ Foam::ifstreamPointer::ifstreamPointer
 
         const fileName pathname_gz(pathname + ".gz");
 
-        if (isFile(pathname_gz, false))
+        if (Foam::isFile(pathname_gz, false))
         {
             #ifdef HAVE_LIBZ
 
@@ -128,13 +98,29 @@ Foam::ifstreamPointer::ifstreamPointer
 
             #endif /* HAVE_LIBZ */
         }
+        else
+        {
+            // TBD:
+            // Can also fallback and open .orig files too
+            //
+            // auto* file = dynamic_cast<std::ifstream*>(ptr_.get());
+            // file->open(pathname + ".orig", mode);
+        }
     }
 }
 
 
+Foam::ofstreamPointer::ofstreamPointer() noexcept
+:
+    ptr_(),
+    atomic_(false)
+{}
+
+
 Foam::ofstreamPointer::ofstreamPointer(std::nullptr_t)
 :
-    ptr_(new Foam::ocountstream)
+    ptr_(new Foam::ocountstream),
+    atomic_(false)
 {}
 
 
@@ -142,10 +128,12 @@ Foam::ofstreamPointer::ofstreamPointer
 (
     const fileName& pathname,
     IOstreamOption::compressionType comp,
-    const bool append
+    const bool append,
+    const bool atomic
 )
 :
-    ptr_(nullptr)
+    ptr_(nullptr),
+    atomic_(atomic)
 {
     std::ios_base::openmode mode
     (
@@ -155,18 +143,56 @@ Foam::ofstreamPointer::ofstreamPointer
     if (append)
     {
         mode |= std::ios_base::app;
+
+        // Cannot append to gzstream
+        comp = IOstreamOption::UNCOMPRESSED;
+
+        // Cannot use append + atomic operation, without lots of extra work
+        atomic_ = false;
     }
 
+
+    // When opening new files, remove file variants out of the way.
+    // Eg, opening "file1"
+    // - remove old "file1.gz" (compressed)
+    // - also remove old "file1" if it is a symlink and we are not appending
+    //
+    // Not writing into symlinked files avoids problems with symlinked
+    // initial fields (eg, 0/U -> ../0.orig/U)
+
     const fileName pathname_gz(pathname + ".gz");
+    const fileName pathname_tmp(pathname + "~tmp~");
+
+    fileName::Type fType = fileName::Type::UNDEFINED;
 
     if (IOstreamOption::COMPRESSED == comp)
     {
-        // Output compression requested
+        // Output compression requested.
 
         #ifdef HAVE_LIBZ
+        // TBD:
+        // atomic_ = true;  // Always treat COMPRESSED like an atomic
 
-        removeConflictingFiles(pathname, append, pathname_gz);
-        ptr_.reset(new ogzstream(pathname_gz, mode));
+        const fileName& target = (atomic_ ? pathname_tmp : pathname_gz);
+
+        // Remove old uncompressed version (if any)
+        fType = Foam::type(pathname, false);
+        if (fType == fileName::SYMLINK || fType == fileName::FILE)
+        {
+            Foam::rm(pathname);
+        }
+
+        // Avoid writing into symlinked files (non-append mode)
+        if (!append || atomic_)
+        {
+            fType = Foam::type(target, false);
+            if (fType == fileName::SYMLINK)
+            {
+                Foam::rm(target);
+            }
+        }
+
+        ptr_.reset(new ogzstream(target, mode));
 
         #else /* HAVE_LIBZ */
 
@@ -181,43 +207,51 @@ Foam::ofstreamPointer::ofstreamPointer
         #endif /* HAVE_LIBZ */
     }
 
-    if (IOstreamOption::UNCOMPRESSED == comp)
+    if (IOstreamOption::COMPRESSED != comp)
     {
-        removeConflictingFiles(pathname_gz, append, pathname);
-        ptr_.reset(new std::ofstream(pathname, mode));
+        const fileName& target = (atomic_ ? pathname_tmp : pathname);
+
+        // Remove old compressed version (if any)
+        fType = Foam::type(pathname_gz, false);
+        if (fType == fileName::SYMLINK || fType == fileName::FILE)
+        {
+            Foam::rm(pathname_gz);
+        }
+
+        // Avoid writing into symlinked files (non-append mode)
+        if (!append || atomic_)
+        {
+            fType = Foam::type(target, false);
+            if (fType == fileName::SYMLINK)
+            {
+                Foam::rm(target);
+            }
+        }
+
+        ptr_.reset(new std::ofstream(target, mode));
     }
 }
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-void Foam::ifstreamPointer::reopen_gz(const std::string& pathname_gz)
+void Foam::ifstreamPointer::reopen_gz(const std::string& pathname)
 {
     #ifdef HAVE_LIBZ
-    igzstream* gz = dynamic_cast<igzstream*>(ptr_.get());
+    auto* gz = dynamic_cast<igzstream*>(ptr_.get());
 
     if (gz)
     {
         // Special treatment for gzstream
         gz->close();
         gz->clear();
-        gz->open(pathname_gz);
-    }
-    #endif /* HAVE_LIBZ */
-}
 
-
-void Foam::ofstreamPointer::reopen_gz(const std::string& pathname_gz)
-{
-    #ifdef HAVE_LIBZ
-    ogzstream* gz = dynamic_cast<ogzstream*>(ptr_.get());
-
-    if (gz)
-    {
-        // Special treatment for gzstream
-        gz->close();
-        gz->clear();
-        gz->open(pathname_gz);
+        gz->open
+        (
+            pathname + ".gz",
+            (std::ios_base::in | std::ios_base::binary)
+        );
+        return;
     }
     #endif /* HAVE_LIBZ */
 }
@@ -225,7 +259,36 @@ void Foam::ofstreamPointer::reopen_gz(const std::string& pathname_gz)
 
 void Foam::ofstreamPointer::reopen(const std::string& pathname)
 {
-    std::ofstream* file = dynamic_cast<std::ofstream*>(ptr_.get());
+    #ifdef HAVE_LIBZ
+    auto* gz = dynamic_cast<ogzstream*>(ptr_.get());
+
+    if (gz)
+    {
+        // Special treatment for gzstream
+        gz->close();
+        gz->clear();
+
+        if (atomic_)
+        {
+            gz->open
+            (
+                pathname + "~tmp~",
+                (std::ios_base::out | std::ios_base::binary)
+            );
+        }
+        else
+        {
+            gz->open
+            (
+                pathname + ".gz",
+                (std::ios_base::out | std::ios_base::binary)
+            );
+        }
+        return;
+    }
+    #endif /* HAVE_LIBZ */
+
+    auto* file = dynamic_cast<std::ofstream*>(ptr_.get());
 
     if (file)
     {
@@ -234,7 +297,69 @@ void Foam::ofstreamPointer::reopen(const std::string& pathname)
             file->close();
         }
         file->clear();
-        file->open(pathname);
+
+        // Don't need original request to append since rewind implies
+        // trashing that anyhow.
+
+        if (atomic_)
+        {
+            file->open
+            (
+                pathname + "~tmp~",
+                (std::ios_base::out | std::ios_base::binary)
+            );
+        }
+        else
+        {
+            file->open
+            (
+                pathname,
+                (std::ios_base::out | std::ios_base::binary)
+            );
+        }
+        return;
+    }
+}
+
+
+void Foam::ofstreamPointer::close(const std::string& pathname)
+{
+    if (!atomic_ || pathname.empty()) return;
+
+    #ifdef HAVE_LIBZ
+    auto* gz = dynamic_cast<ogzstream*>(ptr_.get());
+
+    if (gz)
+    {
+        // Special treatment for gzstream
+        gz->close();
+        gz->clear();
+
+        std::rename
+        (
+            (pathname + "~tmp~").c_str(),
+            (pathname + ".gz").c_str()
+        );
+        return;
+    }
+    #endif /* HAVE_LIBZ */
+
+    auto* file = dynamic_cast<std::ofstream*>(ptr_.get());
+
+    if (file)
+    {
+        if (file->is_open())
+        {
+            file->close();
+        }
+        file->clear();
+
+        std::rename
+        (
+            (pathname + "~tmp~").c_str(),
+            pathname.c_str()
+        );
+        return;
     }
 }
 
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
index cc2d5a472a..88e6657b0d 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
@@ -83,7 +83,7 @@ void Foam::masterOFstream::checkWrite
     const std::string& s
 )
 {
-    checkWrite(fName, &s[0], s.length());
+    checkWrite(fName, s.data(), s.length());
 }
 
 
@@ -126,7 +126,7 @@ void Foam::masterOFstream::commit()
             string s(this->str());
             this->reset();
 
-            os.write(&s[0], s.length());
+            os.write(s.data(), s.length());
         }
 
         labelList recvSizes;
@@ -179,7 +179,7 @@ Foam::masterOFstream::masterOFstream
 (
     const fileName& pathName,
     IOstreamOption streamOpt,
-    const bool append,
+    IOstreamOption::appendType append,
     const bool valid
 )
 :
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.H b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.H
index 2c2f9c3667..7971ddea91 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.H
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.H
@@ -55,11 +55,14 @@ class masterOFstream
 {
     // Private Data
 
+        //- The backend file name
         const fileName pathName_;
 
+        //- Output file compression
         const IOstreamOption::compressionType compression_;
 
-        const bool append_;
+        //- Open file in append mode
+        const IOstreamOption::appendType append_;
 
         //- Should file be written
         const bool valid_;
@@ -91,7 +94,7 @@ public:
         (
             const fileName& pathname,
             IOstreamOption streamOpt = IOstreamOption(),
-            const bool append = false,
+            IOstreamOption::appendType append = IOstreamOption::NON_APPEND,
             const bool valid = true
         );
 
diff --git a/src/OpenFOAM/db/IOstreams/IOstreams/IOstream.C b/src/OpenFOAM/db/IOstreams/IOstreams/IOstream.C
index c126ab1d99..983c3a7275 100644
--- a/src/OpenFOAM/db/IOstreams/IOstreams/IOstream.C
+++ b/src/OpenFOAM/db/IOstreams/IOstreams/IOstream.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2018-2021 OpenCFD Ltd.
+    Copyright (C) 2018-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
diff --git a/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.C b/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.C
index a4d5255ee2..9be225b51c 100644
--- a/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.C
+++ b/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.C
@@ -26,7 +26,7 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "IOstreamOption.H"
-#include "error.H"
+#include "debug.H"
 #include "dictionary.H"
 #include "Enum.H"
 #include "Switch.H"
diff --git a/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.H b/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.H
index 29bfd3c0b0..5b16cd3e3d 100644
--- a/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.H
+++ b/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2018-2021 OpenCFD Ltd.
+    Copyright (C) 2018-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -36,6 +36,9 @@ Description
     The compression (UNCOMPRESSED | COMPRESSED) is typically controlled
     by switch values (true/false, on/off, ...).
 
+    Additionally, some enumerations are defined (APPEND, NON_APPEND, ...)
+    that are useful, verbose alternatives to bool values.
+
 SourceFiles
     IOstreamOption.C
 
@@ -80,6 +83,20 @@ public:
             COMPRESSED          //!< compression = true
         };
 
+        //- File appending (NON_APPEND | APPEND)
+        enum appendType : char
+        {
+            NON_APPEND = 0,     //!< append = false
+            APPEND              //!< append = true
+        };
+
+        //- Atomic operations (output)
+        enum atomicType : char
+        {
+            NON_ATOMIC = 0,     //!< atomic = false
+            ATOMIC              //!< atomic = true
+        };
+
 
         //- Representation of a major/minor version number
         class versionNumber
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
index 9061999e69..3c2404bd02 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017-2018 OpenFOAM Foundation
-    Copyright (C) 2019-2021 OpenCFD Ltd.
+    Copyright (C) 2019-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -51,7 +51,7 @@ bool Foam::OFstreamCollator::writeFile
     const labelUList& recvSizes,
     const PtrList<SubList<char>>& slaveData,    // optional slave data
     IOstreamOption streamOpt,
-    const bool append,
+    IOstreamOption::appendType append,
     const dictionary& headerEntries
 )
 {
@@ -79,7 +79,7 @@ bool Foam::OFstreamCollator::writeFile
         osPtr.reset(new OFstream(fName, streamOpt, append));
         auto& os = *osPtr;
 
-        if (!append)
+        if (append == IOstreamOption::NON_APPEND)
         {
             // No IOobject so cannot use IOobject::writeHeader
 
@@ -348,7 +348,7 @@ bool Foam::OFstreamCollator::write
     const fileName& fName,
     const string& data,
     IOstreamOption streamOpt,
-    const bool append,
+    IOstreamOption::appendType append,
     const bool useThread,
     const dictionary& headerEntries
 )
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H
index dfcfdae236..3285e9eb7b 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.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.
@@ -48,8 +48,8 @@ SourceFiles
 
 \*---------------------------------------------------------------------------*/
 
-#ifndef OFstreamCollator_H
-#define OFstreamCollator_H
+#ifndef Foam_OFstreamCollator_H
+#define Foam_OFstreamCollator_H
 
 #include <thread>
 #include <mutex>
@@ -81,7 +81,7 @@ class OFstreamCollator
             const labelList sizes_;
             PtrList<List<char>> slaveData_;
             const IOstreamOption streamOpt_;
-            const bool append_;
+            IOstreamOption::appendType append_;
             const dictionary headerEntries_;
 
             writeData
@@ -92,7 +92,7 @@ class OFstreamCollator
                 const string& data,
                 const labelList& sizes,
                 IOstreamOption streamOpt,
-                const bool append,
+                IOstreamOption::appendType append,
                 const dictionary& headerEntries
             )
             :
@@ -157,7 +157,7 @@ class OFstreamCollator
             const labelUList& recvSizes,
             const PtrList<SubList<char>>& slaveData,
             IOstreamOption streamOpt,
-            const bool append,
+            IOstreamOption::appendType append,
             const dictionary& headerEntries
         );
 
@@ -200,7 +200,7 @@ public:
             const fileName&,
             const string& data,
             IOstreamOption streamOpt,
-            const bool append,
+            IOstreamOption::appendType append,
             const bool useThread = true,
             const dictionary& headerEntries = dictionary::null
         );
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
index 540163a01f..edfbec5563 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
@@ -217,13 +217,17 @@ bool Foam::fileOperations::collatedFileOperation::appendObject
 
     // Note: cannot do append + compression. This is a limitation
     // of ogzstream (or rather most compressed formats)
+    //
+    // File should always be created as non-atomic
+    // (consistency between append/non-append)
 
     OFstream os
     (
         pathName,
-        // UNCOMPRESSED
+        // UNCOMPRESSED (binary only)
         IOstreamOption(IOstreamOption::BINARY, streamOpt.version()),
-        !isMaster  // append slaves
+        // Append on sub-ranks
+        (isMaster ? IOstreamOption::NON_APPEND : IOstreamOption::APPEND)
     );
 
     if (!os.good())
@@ -381,7 +385,7 @@ bool Foam::fileOperations::collatedFileOperation::writeObject
         (
             pathName,
             streamOpt,
-            false,  // append=false
+            IOstreamOption::NON_APPEND,
             valid
         );
 
@@ -424,7 +428,7 @@ bool Foam::fileOperations::collatedFileOperation::writeObject
             (
                 pathName,
                 streamOpt,
-                false,  // append=false
+                IOstreamOption::NON_APPEND,
                 valid
             );
 
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C
index e0793a4307..bf8e046e74 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C
@@ -59,7 +59,7 @@ Foam::threadedCollatedOFstream::~threadedCollatedOFstream()
         pathName_,
         str(),
         IOstreamOption(IOstreamOption::BINARY, version(), compression_),
-        false,  // append=false
+        IOstreamOption::NON_APPEND,
         useThread_,
         headerEntries_
     );
diff --git a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C
index d6c071cd84..5205de0043 100644
--- a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C
@@ -2455,7 +2455,7 @@ Foam::fileOperations::masterUncollatedFileOperation::NewOFstream
         (
             pathName,
             streamOpt,
-            false,  // append=false
+            IOstreamOption::NON_APPEND,
             valid
         )
     );
diff --git a/src/fileFormats/ensight/file/ensightFile.C b/src/fileFormats/ensight/file/ensightFile.C
index 4214b726df..bd39b34b0a 100644
--- a/src/fileFormats/ensight/file/ensightFile.C
+++ b/src/fileFormats/ensight/file/ensightFile.C
@@ -79,7 +79,7 @@ Foam::ensightFile::ensightFile
     IOstreamOption::streamFormat fmt
 )
 :
-    OFstream(ensight::FileName(pathname), fmt)
+    OFstream(IOstreamOption::ATOMIC, ensight::FileName(pathname), fmt)
 {
     init();
 }
@@ -92,7 +92,7 @@ Foam::ensightFile::ensightFile
     IOstreamOption::streamFormat fmt
 )
 :
-    OFstream(path/ensight::FileName(name), fmt)
+    OFstream(IOstreamOption::ATOMIC, path/ensight::FileName(name), fmt)
 {
     init();
 }
diff --git a/src/fileFormats/ensight/file/ensightFile.H b/src/fileFormats/ensight/file/ensightFile.H
index ddf866c86d..6f63148fe2 100644
--- a/src/fileFormats/ensight/file/ensightFile.H
+++ b/src/fileFormats/ensight/file/ensightFile.H
@@ -92,7 +92,7 @@ public:
     // Static Functions
 
         //- Return a null ensightFile
-        inline static const ensightFile& null()
+        static const ensightFile& null()
         {
             return NullObjectRef<ensightFile>();
         }
@@ -102,6 +102,7 @@ public:
 
         //- Construct from path-name.
         //  The path-name is adjusted for valid ensight file naming.
+        //  Always created as an atomic
         explicit ensightFile
         (
             const fileName& pathname,
@@ -110,6 +111,7 @@ public:
 
         //- Construct from path and name.
         //  Only the name portion is adjusted for valid ensight file naming.
+        //  Always created as an atomic
         ensightFile
         (
             const fileName& path,
diff --git a/src/fileFormats/ensight/file/ensightGeoFile.H b/src/fileFormats/ensight/file/ensightGeoFile.H
index d18fbe0fcb..9fbc124902 100644
--- a/src/fileFormats/ensight/file/ensightGeoFile.H
+++ b/src/fileFormats/ensight/file/ensightGeoFile.H
@@ -67,7 +67,7 @@ public:
     // Static Functions
 
         //- Return a null ensightGeoFile
-        inline static const ensightGeoFile& null()
+        static const ensightGeoFile& null()
         {
             return NullObjectRef<ensightGeoFile>();
         }
diff --git a/src/lumpedPointMotion/movement/lumpedPointMovement.C b/src/lumpedPointMotion/movement/lumpedPointMovement.C
index dcfc841ad2..5c23a55c3a 100644
--- a/src/lumpedPointMotion/movement/lumpedPointMovement.C
+++ b/src/lumpedPointMotion/movement/lumpedPointMovement.C
@@ -1314,7 +1314,7 @@ bool Foam::lumpedPointMovement::writeData
         (
             coupler().resolveFile(logName_),
             IOstreamOption(),
-            true  // append
+            IOstreamOption::APPEND
         );
 
         writeData(os, forces, moments, outputFormatType::PLAIN, timesWritten);