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

       /ABORT_VIRTUAL_UNIT DSAnnnn:

    Aborts mount verification.

    To use this qualifier, the shadow set must be in mount
    verification. When you specify this qualifier, the shadow set
    aborts mount verification immediately on the node from which the
    qualifier is issued. Use this qualifier when it is known that the
    unit cannot be recovered.

    Note that after this command completes, the shadow set must still
    be dismounted. Use the following command to dismount the shadow
    set:

    $ DISMOUNT/ABORT DSAnnnn: