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

       /FAST_SKIP=option

    Allows you to skip by file mark or by record.

                                   NOTE

       This tape positioning qualifier is for use on local SCSI
       tape drives only.

    PER_IO          Allows a local MK device to use the skip-by-
    (default)       filemarks function. The tape drive must be able
                    to do a SCSI READ POSITION command and report
                    blank check at end-of-data. The IO$M_ALLOWFAST
                    function modifier must be supplied with IO$_
                    SKIPFILE. Otherwise, the tape will skip files
                    using the skip-by-records function.

    ALWAYS          Allows a local MK device to use the skip-by-
                    filemarks function. The tape drive must be able
                    to support the skip-by-filemarks function, and
                    no modifications should be needed to the IO$_
                    SKIPFILE function.

    NEVER           Specifies that a local MK device skip only by
                    records. If you use a utility that depends on the
                    semantics of skipping with skip-records, you may
                    also need to use this option because it causes
                    BACKUP or COPY to use the previous positioning.