Re: Recommended CPU % utilized -- MIDRANGE-L

Bruce Hoffman wrote:
>Pete Hall wrote:
>> 
>> What indicators can be used to justify or shoot down a proposal to upgrade
>> CPU? Are there any published recommendations anywhere? Digging through the
>> work management guide didn't turn up anything. About all I could come up
>> with is a bar chart that shows the percent of time that CPU utilization was
>> above x%. Subjectively, I know that when it goes over 90%, interactive
>> response starts to deteriorate, and since we have tuned batch to favor
>> interactive response time, I suspect that batch starts to deteriorate as
>> soon as utilization gets over 50-60%, with major throughput degradation by
>> the time it reaches 80%. I have not done any benchmarks on this yet. That's
>> my probable next step.
>> 
>
>What you are asking is more complicated than you might expect. When it
>comes to CPU upgrades, you are really looking for the amount of time
>that processes must WAIT to get the CPU and then remove the IO waits
>from the equation.
>
>If you don't have the performance tools LP, then determination yea or
>nea will be purely subjective.
>
>If you have the tools, then you need to monitor around the time of heavy
>CPU use and then look in the reports for the jobs waiting for CPU. This
>is based on "Queueing Theory" and, if I remember correctly, there is an
>appendix for that topic in the Performance Guide.
>
>Actually modelling the performance, verifying the model and then
>upgrading the CPU in the Performance Tools is the best way to do this
>and is one of the reasons that everyone with an AS/400 that COULD grow
>should be running regular collections (and I don't mean the PM/400
>Marketing junk).
>
>You should know the batch/interactive workload mix, the peak utilization
>rates of disk, IO and CPU based on time of year and time of week, all
>off the top of your head. If you run the tools regularly, produce the
>summary reports weekly and spend an hour each week quickly reviewing
>them, you can do this. Then the question you are asking is only one or
>two monitor sessions and three or four hours of modelling work away.
>

The  Snapshot/400 product (I am a user not a sales person) allows you to
see the effect of hardware upgrades on your current workload on the fly. It
is well worth a look for "what-if" upgrade type scenarios in my opinion.

It graphs CPU use (broken up by batch/interactive/system) on an on-going
basis, in a bar chart format every 2 minutes (real time) so that you can
atually see what is happening to your machine workload as it happens. It
also allows you to model the likely effect of a cpu upgrade on your current
workload (you specify the model of the upgrade and it alters the bar chart
on the fly) and to also tweak the parameters of your workload if I remember
correctly (eg increase workload 10%)

I think the homepage is at www.midcomp.com.au

It sure takes the pain out of wading though all that performance tools stuff.

Hops this helps.
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