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

       /ALIAS save-set-spec (default)
       /NOALIAS

    Command Qualifier

    Specifies that the previous behavior of multiple processing
    of alias and primary file entries be maintained. The /ALIAS
    qualifier maintains the previous BACKUP behavior of treating
    alias file entries the same as primary file entries. Therefore, a
    primary file may be processed multiple times by BACKUP if one or
    more alias file entries reference the same primary file entry.

    If you specify /NOALIAS, alias directory and file entries are
    ignored. Therefore, multiple processing of primary files may be
    avoided, which saves time and save-set file space. If a restore
    operation is performed using the /ALIAS qualifier but the save
    set was created by using the /NOALIAS qualifier, a message is
    displayed that the /ALIAS qualifier will be ignored.