How a subsystem handles several job queues

To illustrate how a subsystem handles several job queues, consider this scenario.

• Job Queue A (SEQNBR=10)
• Job 1
• Job 2
• Job 3
• Job Queue B (SEQNBR=20)
• Job 4
• Job 5
• Job 6
• Job Queue C (SEQNBR=30)
• Job 7
• Job 8
• Job 9

Each job queue entry in this scenario is specified as MAXACT(*NOMAX). The subsystem first selects jobs from job queue A because the job queue entry has the lowest sequence number. If the maximum number of jobs in the subsystem is 3 (MAXJOBS(3) parameter on the Create Subsystem Description (CRTSBSD) command), it can select all the jobs from job queue A to be active at the same time.

When any of the three jobs is completed, the activity level is no longer at the maximum; therefore a new job is selected from job queue B because it has the next lowest sequence number (assuming no new jobs have been added to job queue A). Because each job queue entry specifies MAXACT(*NOMAX), the MAXACT value does not prevent jobs from being started. Had each job queue entry specified MAXACT(1), then jobs 1, 4, and 7 would have been started. Had job queue entry A been specified as MAXACT(2), then jobs 1, 2, and 4 would have been started.