Basically, there are no requirements for establishing a specific type of user ID. That is, in some installations, you might form user IDs by adding a numerical suffix to a group name (for example, ADMIN01 or MKT06). In other cases, you might use first names (for example, PETER and PAUL could be defined and connected to the RESEARCH group. In this case, if PETER subsequently leaves the RESEARCH group to join the TEST group, he need not change his user ID.)

The concept of user IDs based on group names appears practical because a quick glance at the user ID reveals the group. However, this concept might not prove so practical a few years later if many of the current users have changed groups. In addition, how does such a user handle their user data sets (data sets with the user ID as the high-level qualifier) after the user ID is changed? In the long run, user IDs based on something like user names or personnel numbers do not have this problem and offer the greatest long-term flexibility.

For suggestions related to z/OS UNIX, see Defining user identifiers (UIDs).