To respond to system problems when other consoles fail or are unavailable, you can activate problem determination (PD) mode manually or automatically (for diagnosis purposes, PD mode expands message processing for the system console). To manually activate and deactivate PD mode, use the VARY CN,ACTIVATE and VARY CN,DEACTIVATE commands, respectively. To set up the system console to automatically activate and deactivate PD mode, use the VARY CN,AUTOACT= command (see Using AUTOACT with the system console.)
For details on the syntax and usage of VARY CN,ACTIVATE, VARY CN,DEACTIVATE, and VARY CN,AUTOACT=, see z/OS MVS System Commands.