The RACF® component of the Security Server authenticates users and verifies whether they are allowed to access certain resources. An equivalent security product can be used to do those tasks.

A user is identified by a UID, which is kept in the OMVS segment of the RACF user profile, and a GID, which is kept in the OMVS segment of the RACF group profile. z/OS Security Server RACF Security Administrator's Guide contains information about OMVS segments.