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

       /CACHE[=(keyword[,...])]

    Displays information about the Virtual I/O Cache facility or
    the Extended File Cache facility, depending on which is loaded.
    The Cache facility information is displayed as part of the SHOW
    MEMORY and SHOW MEMORY/CACHE/FULL commands.

    If the Extended File Cache is loaded, you can specify the
    following keywords and options:

    VOLUME[=device] Requests display of volume-level statistics
                    for the specified volume(s). If no device
                    is specified, defaults to SYS$DISK. Device
                    specifications may be wildcarded; if so, the
                    device specification must be based on the
                    physical device name. Specify VOLUME=* to see
                    statistics for all volumes in cache.
    FILE=filespec   Requests display of file-level statistics for
                    the specified file(s) in cache. The filespec
                    must contain an explicit or implicit device
                    specification. The filespec may be wildcarded
                    according to RMS rules. Specify FILE=dev:*.*
                    to see statistics for all files in cache for a
                    device. Partially wild file specifications that
                    are satisfied by large numbers of files on disk
                    may incur significant processing overhead during
                    display. By default, both open and closed files
                    are displayed (use the OPEN and CLOSED keywords
                    to further restrict which files are displayed).

                    Note that this command may fail if you select a
                    large number of files for display. If you receive
                    an error message, reduce the number of selected
                    files and reissue the command.
    TOPQIO[=n]      Requests display of file-level statistics for
                    the n files in cache with the highest overall QIO
                    count (n defaults to 10).
    TOPHITRATE[=n]  Requests display of file-level statistics for the
                    n files in cache with the highest overall cache
                    hit rate (n defaults to 10).
                    OPEN      Include only open files in the display
                              (default for TOPQIO and TOPHITRATE).
                    CLOSED    Include only closed files in the
                              display.