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

       /TRUNCATE_USER_NAME[=n]
       /NOTRUNCATE_USER_NAME

    Optional. Default: no truncation.

    Truncates the user name to the specified number of characters. If
    you omit n, the default is eight characters.