The lifecycle of the administrative task scheduler

The administrative task scheduler starts as a task on the z/OS system during Db2 startup or initialization. The administrative task scheduler remains active unless it is explicitly stopped, even when Db2 terminates.

Every Db2 subsystem has a coordinated administrative task scheduler address space that it can start with a z/OS started task procedure.

Two instances of the same administrative task scheduler cannot run simultaneously. To avoid starting up a duplicate administrative task scheduler, at startup the administrative task scheduler checks that there is no address space other than itself with the same name. If another address space with the same name is active, then the new administrative task scheduler immediately shuts down and displays a console message (DSNA674I). The administrative task scheduler can check the address spaces only in the same system, not the entire Sysplex.

When Db2 terminates, the administrative task scheduler remains active so that scheduled JCL jobs can run. When Db2 starts again, it connects to the administrative task scheduler automatically. It does not need to be restarted.

Figure 1. The lifecycle of the administrative task scheduler
Begin figure description. This figure shows the lifecycle of the administrative task scheduler as described in this topic. End figure description.

If you want the administrative task scheduler to terminate when Db2 is stopped, you can specify the STOPONDB2STOP parameter in the started task before restarting the administrative task scheduler. This parameter has no value. You specify this parameter by entering STOPONDB2STOP without an equal sign (=) or a value. When you specify this parameter, the administrative task scheduler terminates after it finishes executing the tasks that are running and after executing the tasks that are triggered by Db2 stopping. When Db2 starts again, the administrative task scheduler is restarted.

Important: When you use the STOPONDB2STOP parameter to stop the administrative task scheduler when Db2 is stopped, JCL tasks will not run. These JCL tasks will not run, even if they could have run successfully had an administrative task scheduler remained active.