VMS Help TCPIP Services, Programming Interfaces, RPC Client Routines, authunix_create, Arguments  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 host
    Pointer to the name of the host on which the information was
    created. This is usually the name of the system running the
    client process.
 uid
    The user's user identification.
 gid
    The user's current group.
 len
    The number of elements in aup_gids array.
                                   NOTE
       This parameter is ignored by the product's RPC
       implementation.
 aup_gids
    A pointer to an array of groups to which the user belongs.
                                   NOTE
       This parameter is ignored by the product's RPC
       implementation.