/sys$common/syshlp/helplib.hlb SET, FILE, Qualifiers, /CACHING_ATTRIBUTE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /CACHING_ATTRIBUTE=keyword

    Use this qualifier to control which files are cached by the
    Extended File Cache. It sets the caching attribute for a file
    or directory in a Files-11 ODS-2 or ODS-5 volume.

    The caching attribute of a file is the default caching option
    that is used by the Extended File Cache when an application
    accesses the file without specifying which caching option it
    wants to use.

    The keyword can be either WRITETHROUGH or NO_CACHING. Use
    WRITETHROUGH for files that you want to be cached. Use NO_CACHING
    for files that you don't want to be cached.

    The Extended File Cache does not cache directories. The caching
    attribute of a directory controls only how the caching attribute
    is inherited by new files and subdirectories created in the
    directory:

    o  When you create a new directory or file, it inherits its
       caching attribute from its parent directory.

    o  When you create a new version of an existing file, the new
       file inherits its caching attribute from the highest version
       of the existing file.

    When you use the INITIALIZE command to create a new Files-
    11 volume, the caching attribute of its root directory
    (000000.DIR;1) is set to write-through. This means that by
    default, all the files and directories you create in the volume
    will inherit a caching attribute of write-through unless you use
    SET FILE /CACHING_ATTRIBUTE.

    If you do not want to cache any files in a volume, mount the
    volume with caching disabled, using MOUNT /NOCACHE, instead of
    setting the caching attribute of all the files in the volume to
    NO_CACHING. Using MOUNT /NOCACHE gives better performance, and
    ensures the minimum caching overhead.

    When you change the caching attribute of a directory, it does
    not affect the caching attribute of any existing files and
    subdirectories in the directory.

    When you change the caching attribute of a file, it does not
    affect the type of caching being used by any applications that
    are currently accessing the file.