CA Top Secret and RACF have similar functionality but it is administered in a different way.
In RACF, you put the GID on a GROUP.
In CA Top Secret, it is done differently. GROUPS in RACF is equivalent to PROFILEs in TSS.
GROUPs in CA Top Secret is how you assign an GID to a user. You cannot assign a GID to multiple GROUPs.
In CA Top Secret, you dont put GIDs directrly on an acid. You assign the GID to a GROUP type acid. Then you take that GROUP type acid and TSS ADD it to whoever acid you want to give the GID. That is how it is done in CA Top Secret.
TSS ADD(OMVSGRP) GID(123)
TSS ADD(USERA) GROUP(OMVSGRP)
Yes its different than the way RACF does it, but achieves the same objective as RACF.