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

       /UNLOAD
       /NOUNLOAD

    Determines whether the device on which the volume is mounted is
    physically unloaded. If you specify the DISMOUNT command without
    the /UNLOAD or the /NOUNLOAD qualifier, the qualifier that you
    specified with the MOUNT command (either /UNLOAD or /NOUNLOAD)
    determines whether the volume is unloaded physically.