When you start debugging by choosing to debug an existing job, you can specify a job that is active, on hold, or in a job queue that is on hold. The System Debugger automatically performs the necessary steps to release (but not start) a held job or job queue.
When you start debugging operations on a held job, the System Debugger asks you to confirm that you want to release the job or the job queue.
In some cases, you may want to manually start a job, put the job on hold (or start the job in a job queue that is on hold), and then begin debugging the program associated with that job.