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

       /USER_NAME=remote_user_name

    Optional. Default: current name on local host in lowercase.

    Specify user name on the source or destination remote host.
    Use only if an entry allowing access to this user has not been
    added to the remote host's authentication files. You must also
    specify the /PASSWORD qualifier with the /USER_NAME qualifier.
    If necessary, truncate the user name to the required number of
    characters using the /TRUNCATE_USER_NAME qualifier. Specifying
    "username@" with the source or destination parameter is the
    equivalent UNIX style method.