When managing the jobs on an AS/400, iSeries or IBM i power system box you may be familiar or not with the priorities of how the jobs run. But sometimes people confuse the different types of priorities that are available to tune the performance of the jobs. It’s important to understand and distinguish the different priorities.
First up let’s look at a print screen of the work with active jobs displays showing the jobs RUN PRIORITY
Look at the column labeled “PTY” … To see this column you have to press F11 from the WRKACTJOB display
So the jobs RUN PRIORITY (emphasis added) allows the higher priority jobs (in this case it’s sort of counter intuitive because the priorities go from lowest to highest, so 99 would be very low and 1 would be high priority) to get the best service from the CPU.
So sometimes it helps to crank up the job priority for a job that needs extra processing resources, technically it only needs to be one level higher than the other jobs in the same subsystem. Typically batch jobs run at priority 50 and interactive runs at priority 20 because you don’t want green screen folks waiting a long time while reports can crank away in the background without using up a bunch of system resources.
Now let’s look at a job priority. This is a totally different thing from the run priority we just discussed. The job priority is how a job is sequenced to run while it’s waiting in a job queue. Here is a print screen from the WRKJOBQ command.
These priorities rank from 1 to 9 with 1 being the highest priority.
As you can see from the print screen “JOB1″ has a job priority of 6 which puts it at the bottom of the job queue. So JOB1 will wait until jobs JOB2 and JOB3 have run before it get’s submitted to the subsystem for processing. Also if another job with a higher job priority is placed in the job queue it will still wait it’s turn to run.
Often times people will want to be able to change the run priority of a job, this is accomplished by changing the subsystem configuration including the job description used. But that’s an article for another day.
Another area you will see priorities like this are in the output queues with spool files and they function similarly.
John Andersen is an IT manager and ten year veteran of the AS/400 platform. If you liked this article then you will be interested in his Power System Jump Start course. You can claim your copy today by logging on to http://www.midrangejumpstart.com
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