Uniquely identifies each user on the system.

    The user identifier consists of the standard OpenVMS user
    identification code (UIC), a group name, and a member name (user
    name). The group name is optional. The user identifier can be
    in either numeric or alphanumeric format. The following are all
    valid user identifiers that could identify the same user:

       K_JONES
       [SYSTEM3, K_JONES]
       [341,311]

    You can use the asterisk (*)  wildcard character as part of a
    user identifier. For example, if you want to specify all users
    in a group on an OpenVMS system, you can enter [341,*] as the
    identifier.

    When Oracle Rdb creates a database, it automatically creates an
    ACL entry with the identifier [*,*], which grants all privileges
    except DBCTRL to any user.

    You cannot use more than one user identifier in a multiple
    identifier.