We currently run our application programs on an AS/400 Model B35 under V1R3. We have 14 workstations attached to our system, running both interactive and batch programs, and three printers.
Response time was an issue during the late afternoon hours when, of course, everybody wanted to go home by 5 p.m. During these hours it was not uncommon to hear the users say to our system operator, "What are you doing with the system?" Our system operator, performing such duties as backups, restores, running reports, and so on, had no problem with jobs as they were running under priority 10, while all the other users waited somewhere between 30 seconds and 2 minutes between Enters.
Something had to be done, so I started by monitoring all the jobs running in the system with WRKACTJOB and changing their priorities as they ran. I noticed that by changing the system operator to the same level as the interactive users (priority 20), response time improved for those running interactive jobs, while on the other hand the programmer (yours truly) would still complain about response time, especially since I compile my programs in batch (priority 50).
By applying the same criteria, I changed my batch job to priority 20 while it was running. Unfortunately it seemed to have a degrading effect on the system, once again causing the same remarks from the users. I decided to take another approach to the problem. As jobs were running I changed all jobs (interactive, batch, spooling, system control, etc.) to priority 30. This time I was amazed to see that the system response time improved tremendously.
To make a long story short, I made a permanent change to all job priorities to 30 by using the Change Class (CHGCLS) command. The only parameters required are the name of the subsystem (QBASE, QCTL, QSPL, QINTER, etc.) and the library where it resides; the system automatically displays the current values. Of course, you must have the proper authority to the object to make this change. I passed this tip to another shop and they seem quite happy with it. I urge you to try it!
Editor's note: Performance tuning varies greatly depending on the specific application mix. These changes may or may not improve your system performance.