The controlling subsystem

The controlling subsystem is the interactive subsystem that starts automatically when the system starts, and it is the subsystem through which the system operator controls the system via the system console. It is identified in the Controlling subsystem/library (QCTLSBSD) system value.

IBM^® supplies two complete controlling subsystem descriptions: QBASE (the default controlling subsystem) and QCTL. Only one controlling subsystem can be active on the system at any time.

When the system is in the restricted condition, most of the activity on the system has ended, and only one workstation is active. The system must be in this condition for commands such as Save System (SAVSYS) or Reclaim Storage (RCLSTG) to run. Some programs for diagnosing equipment problems also require the system to be in a restricted condition. To end this condition, you must start the controlling subsystem again.

Note: There is also a batch restricted state in which one batch job can be active.

When all of the subsystems, including the controlling subsystem are ended, a restricted condition is created. You can end each subsystem individually or you can use the ENDSBS SBS(*ALL) OPTION(*IMMED).

Important: The system cannot reach the restricted state until there is only one job remaining in the controlling subsystem. Sometimes it may appear as though there is a single job remaining, but the system does not go into the restricted state. In this case you need to verify that there are no suspended system request jobs, suspended group jobs, or disconnected jobs on the remaining active display. Use the Work with Active Jobs (WRKACTJOB) command and press F14=Include to display any suspended or disconnected jobs. If these jobs exist, you need to end them in order for the system to reach the restricted state. The ENDSYS and ENDSBS functions will send a CPI091C information message to the command issuer when this condition is detected.