Displays summary information for each CFB: CFB address, CVB
    address, access count, active I/O count, and file specification
    or ID*.  The /BRIEF qualifier is incompatible with each of the
    /EXTENTS, /FULL, and /STATISTICS qualifiers.

    *If the file specification is available, via LIB$FID_TO_NAME(),
    it is displayed; otherwise, the FID is displayed.  Note that,
    because the volume is accessed through its logical name, if
    two volumes are mounted that have the same logical name (for
    example, one mounted /SYSTEM and one mounted privately, which
    results in the same logical name in two different access-mode
    logical name tables), the incorrect file specification might
    be displayed.