The user might need to change the UID or GID for a file. To protect the data in a file from unauthorized users, the system controls who can change the file access:

• To change the owner (UID) of a file, the superuser can enter a chown command.
• To change the group (GID) of a file, the superuser or the file owner can enter a chgrp command, specifying either a RACF® group name or a GID. The file owner must have the new group as his group or one of his supplementary groups.