VMS Help MOUNT, Qualifiers, /CACHE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

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

    For disks, controls whether caching limits established at system
    generation time are disabled or overridden. With the TAPE_DATA
    option, enables write caching for the tape controller specified
    (if the tape controller supports write caching).

    The following table lists the keywords for this qualifier:

    Keyword       Description

    EXTENT[=n]    Enable or disable extent caching. To enable extent
    and NOEXTENT  caching, you must have the operator user privilege
                  (OPER) and you must specify n, the number of
                  entries in the extent cache. Note that NOEXTENT
                  is equivalent to EXTENT=0; both disable extent
                  caching.

    FILE_ID[=n]   Enable or disable file identification caching.
    and NOFILE_   To enable file identification caching, you must
    ID            have the operator user privilege (OPER) and you
                  must specify n, the number of entries, as a value
                  greater than 1. Note that NOFILE_ID is equivalent
                  to FILE_ID=1; both disable file identification
                  caching.

    LIMIT=n       Specifies the maximum amount of free space in the
                  extent cache in one-thousandths of the currently
                  available free space on the disk.

    QUOTA[=n]     Enable or disable quota caching. To enable quota
    and NOQUOTA   caching, you must have the operator user privilege
                  (OPER) and you must specify n, the number of
                  entries in the quota cache. Normally n is set to
                  the maximum number of active users expected for a
                  disk with quotas enabled. Both NOQUOTA and QUOTA=0
                  disable quota file caching.

    TAPE_DATA     Enables write caching for a magnetic tape device
                  if the tape controller supports write caching. The
                  /CACHE qualifier is the default for mounting tape
                  devices. You must specify TAPE_DATA to enable write
                  caching. If the tape controller does not support
                  write caching, the keyword is ignored.

                  The write buffer stays enabled even after you
                  dismount the magnetic tape. To disable the write
                  buffer, mount a tape with the /NOCACHE qualifier.

                  If a tape supports compaction, then the default
                  is compaction, and caching is enabled. For tape
                  storage devices that support compaction, the
                  following command is valid:

                  $ MOUNT TAPE_DATA/FOREIGN/MEDIA=NOCOMPACTION/NOCACHE

    WRITETHROUGH  Disables the deferred write feature for file
                  headers. By default, this feature is enabled, which
                  improves the performance of applications, such as
                  PATHWORKS, that use it. The deferred write feature
                  is not available on Files-11 ODS-1 volumes.

    Used with the disk options, the /CACHE qualifier overrides
    one or more of the present disk caching limits established at
    system generation time. Used with the TAPE_DATA option, the
    /CACHE qualifier enables write caching for the tape controller
    specified.

    If you do not specify the /CACHE qualifier and it is not implied
    by the use of the qualifier /MEDIA_FORMAT=COMPACTION, caching is
    enabled by default.

    If you specify more than one option, separate them by commas
    and enclose the list in parentheses. The options [NO]EXTENT,
    [NO]FILE_ID, LIMIT, and [NO]QUOTA apply only to a disk device.
    The option TAPE_DATA applies only to a tape device.

    The /NOCACHE qualifier is effective only if compaction is
    not enabled. If compaction is enabled (with the /MEDIA_
    FORMAT=COMPACTION), caching is enabled by default.

    If you specify /NOCACHE for a disk device, all caching is
    disabled for this volume. Note that the /NOCACHE qualifier is
    equivalent to /CACHE=(NOEXTENT,NOFILE_ID,NOQUOTA,WRITETHROUGH).

    If you specify /NOCACHE for a magnetic tape device, the tape
    controller's write cache is disabled for this volume.

    Examples

    The following command mounts an HSG80 Fibre Channel disk
    device labeled FILES and assigns the logical name WORK. The
    /CACHE qualifier enables an extent cache of 60 entries, a file
    identification cache of 60 entries, and a quota cache of 20; it
    disables writeback caching of file headers.

    $ MOUNT/CACHE=(EXTENT=60,FILE_ID=60,QUOTA=20,WRITETHROUGH) -
    _$ $1$DGA0: FILES WORK
    %MOUNT-I-MOUNTED, FILES         mounted on _$1$DGA0: (NODE)

    The following command mounts the volume TAPE on device MUA0 and
    instructs MOUNT to enable the tape controller's write cache for
    MUA0:

    $ MOUNT/CACHE=TAPE_DATA MUA0:  TAPE
    %MOUNT-I-MOUNTED, TAPE  mounted on _NODE$MUA0: