This information assumes that your system includes the RACF® security product. Instead of RACF, your system could have an equivalent security product.

The systems programmer defines a shell user by assigning the user an OMVS user ID (UID) and group ID (GID). These are numeric values associated with a TSO/E user ID; they are set in the RACF user profile and group profile when a user is authorized to use z/OS UNIX services. The system uses the UID and GID to identify the files that a user owns and the processes that a user runs. The UID identifies a user of z/OS UNIX services. The GID is a unique number assigned to a group of related users.

As a user, you can control read, write, and execute access to your files by other users in your group or outside of your group, by setting the permission bits associated with the files.