Re: AS/400 Performance

Gary Munroe <GMUNROE@flemingc.on.ca> wrote:

>What is the best way to find out how the system is performing
>(v3r2)? We seem to be noticing slowdowns but cannot necessarily
>narrow down the cause.  We look at WRKACTJOB to see who
>might be running an intensive job but it doesn't always reflect the
>slowdown we feel.  I know there is performance data collection but
>we are under the impression it makes a big impact on the system
>by itself.  Are there any general maintenance tips we should be
>following?  Also, does a reclaim storage do a defrag to the disks?
>What would?  Would this help?

Gary,

The best single command for detecting a resource hog is WRKSYSACT, which is part
of the performance tools. This shows system tasks as well as jobs and is by
default sequenced in descending order of CPU usage. You can also set it to
refresh the display automatically every few seconds. Only one session can run
WRKSYSACT at a time.

Everywhere I go where there are performance problems it seems that people are
reluctant to collect performance data because they've heard that it has an
impact on system performance. How do you know until you try it? And how can you
analyse the problem without any data? And if you already have poor performance
might it not be worth taking a small extra hit for a limited period in order to
be able to address the problem? It has not been my experience that performance
data collection generally kills the machine.

You don't really need to defrag the disks as such. The system automatically
spreads objects so that the load is balanced between disks. To check that the
load is correctly balanced both in terms of space used and disk accesses look at
WRKDSKSTS. Running performance data collection will give you more information,
however.

Dave Kahn, ABB Steward Ltd.


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