Re: Timeslices

I agree with Alexei - certainly in a BPCS environment reducing the activity
level makes things run noticeably faster, but don't lower it to a level
where you get ineligible jobs. You just need to lower it (to whatever you
calculated from the performance data) and monitor it for a typical business
cycle - i.e. different times of day, different days of week, and don't
forget peak times and month end etc. As a rule of thumb, most of my clients
have it set way too high - 20 or 30 in the interactive pool (because the
system simply divides the memory to come up with a number), and usually
about 7 is a good number.
It's also important if you have SQL, because the optimiser looks at things
like memory available when it decides what method to use for indexing etc.
A low activity level can also help when you are having problems with a
'server' that is maxed out (not enough interactive welly) by constraining
here you avoid the CFINT bottleneck that could kill the whole system. But
obviously it depends on many other things...
Clare

----- Original Message -----
From: "Alexei Pytel" <pytel@us.ibm.com>
To: <midrange-l@midrange.com>
Sent: Saturday, September 01, 2001 12:16 AM
Subject: Re: Timeslices


>
> It depends.
> Sometimes, at some conditions, if activity level is too high, you can
drive
> paging level so high that disk drives will not be able to handle this
load,
> will become a bottleneck, and CPU use and job's progress can actually go
> down.
> One has to take into account other things as well - like jobs' working set
> sizes, I/O activity, throughput of a DASD subsystem and many other...
>
>     Alexei Pytel
>
> "No one can beat unbeatable"
>
>
>
>
>
>                     "Steve Richter"
>                     <srichter@AutoCoder       To:
<midrange-l@midrange.com>
>                     .com>                     cc:
>                     Sent by:                  Subject:     Re: Timeslices
>                     midrange-l-admin@mi
>                     drange.com
>
>
>                     08/31/2001 11:19 AM
>                     Please respond to
>                     midrange-l
>
>
>
>
>
>
> -----Original Message-----
> From: Clare Holtham <Clare.Holtham@btinternet.com>
> To: midrange-l@midrange.com <midrange-l@midrange.com>
> Date: Thursday, August 30, 2001 4:06 AM
> Subject: Re: Timeslices
>
>
> >For the activity level setting, again lower is usually better, but again
> you
> >can calculate the optimum value from Performance Tools data, using the
> >QTRTSUM file and looking at the number of jobs that were in the activity
> >level and the number that went ineligible. The way to do this is to plot
a
>
>
> Clare,
>
> I disagree re setting the activitiy level. Setting it to a low value makes
> likely the condition where jobs are ineligible even though there are cpu
> resources available to run the job. The job mix changes during the day,
> week
> to week, etc. Forcing the activity level to a set value ignores these
> fluctuations.
>
> My solution is to set the interactive activity level high and the
timeslice
> very low.
>
> Steve Richter
>
>
>
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