Your question is not entirely clear.
The only AS/400-related area where I know of control groups being involved is BRMS (Backup Recovery and Media Services).
to work with control groups in BRMS:
GO BRMS -> 2. Backup -> 1. Backup Planning -> 2. Work with Backup Control Groups.
The only other thing I think this could be is the controlling subsystem. This is set in the system value QCTLSBSD.
I would recommend not messing with either of these unless you know what you are doing.