Re: Performance tuning suggestions

At 12:12 AM 2/18/98 -0500, Tim Truax wrote:
>Hello all,
>I have been handed the chore of performance tuning an IBM F50 (192MG
>mem) AS400 at release V3R2.  Any suggestions as to what would be a good
>route for me to follow?  I previously changed the system value QPFRADJ
>to be '2' which means the AS400 can optimize its pools at IPL and at
>radic intervals throughout the day, yet there are some major system bog
>downs still occurring.

Tim,

That's kind of a tall order for a forum like this.

Hopefully, you aren't running controlling subsystem QBASE. If you are, you'll 
need to change the controlling subsystem to QCTL.

Then look at the jobs on your system. Get everything out of *BASE except the 
system jobs. Segregate the user jobs by type (batch/interactive is a good place 
to start), and put each type of job in its own storage pool. Use the 10 
*SHRPOOLs for this. Further subdivide the jobs by priority so that all priority 
30 jobs run together, etc. Let the system performance adjustment move things 
around for a while and see if this gives you acceptable performance.

If it doesn't (which it may not if your system is core bound), turn performance 
adjustment off. Move the memory around so that the swap rates are approximately 
the same in each pool except the system pool, which should be very low (2 or 
less). If you can't get the swap rates down below 15 or so (13 is usually OK), 
you'll need to throttle things back a little bit. Start with the batch pools. 
Decrease activity levels and steal some of the memory for interactive. If you 
absolutely must, decrease the activity level for interactive also, but this can 
cause active jobs to become ineligible, and will cause periodic delays during 
peak periods. It can become a bit of a trick to set activity levels and pool 
sizes for overall acceptable performance and yet prevent thrashing during peak 
loads. When you've got things close, make one change at a time, and watch the 
system run under load to see if things are better or worse.

Moving jobs is accomplished by changing routing data (job descriptions 
primarily, although it can be set with the SBMJOB command also), memory pool 
assignments, routing entries and prestart job entries (subsystem description). 
Priorities are manipulated by changing classes of service (CHGCLS).

If you really haven't messed with this stuff before, I'd recommend paying 
someone to come in and get you started. You don't want to botch it. A day or 
two of a decent consultant's time is worth the expense.

hth
Pete

Pete Hall
peteh@inwave.com 
http://www.inwave.com/~peteh/

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