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

       /ENTER=alias-filespec

    Use with caution.

    Creates an alias for the specified file. Both the original name
    and the new alias refer to the same file. To remove the alias,
    use the SET FILE /REMOVE command.

                                   NOTE

       Make sure that the alias and the original name are in
       different directories, or you may subsequently lose data
       during a delete or purge operation. The DELETE and PURGE
       commands and the file version limit feature can behave
       unpredictably if the original name and the alias are in
       the same directory.

       If you use aliases, you must also be careful when you use
       the DELETE and SET FILE /REMOVE commands, or you may end up
       with either an inaccessable file that has no name or a name
       that does not refer to a file. Follow these guidelines to
       avoid these problems:

       o  Use SET FILE /REMOVE to remove an alias; do not use the
          DELETE command to remove an alias.

       o  Do not use SET FILE /REMOVE to remove the original file
          name.

       If you do not follow these guidelines and encounter
       problems, use ANALYZE /DISK /REPAIR to move inaccessable
       files to the SYSLOST directory and remove names that no
       longer refer to files.