You can assign a z/OS UNIX user identifier (UID) to a RACF® user by specifying a UID value in the OMVS segment of the RACF user profile or by using the AUTOUID keyword.

Rule: When assigning a UID to a user, make sure that the user is connected to at least one group that has an assigned GID. This group should be either the user's default group or one that the user specifies during logon or on the batch job. A user with a UID and a current connect group with a GID can use z/OS UNIX functions and access z/OS UNIX files based on the assigned UID and GID values. If a UID and a GID are not available as described, the user cannot use z/OS UNIX functions.

If you are using NFS, see Assigning UIDs and GIDs in an NFS network for more information.