On Fri, 15 Jan 2010 13:18:04 -0600, Mark Zelden <mark.zel...@zurichna.com>
wrote:

>On Fri, 15 Jan 2010 10:58:46 -0600, Staller, Allan <allan.stal...@kbm1.com>
>wrote:
>
>>I have recently been going through a similar situation with 2 different
>>service classes. Each has the same importance, but different velocities.
>>Each service class can consume all of the available CPU (after online,
>>etc.) at any given time.
>>
>>
>>
>>A review of my performance results has shown that over time, the desired
>>velocities are being achieved. However, the work is not processing as a
>>continuous stream of CPU applied to both service classes. What has been
>>occurring is that during the RMF interval, the 1st service class will
>>consume all available CPU and the 2nd will receive none. A short time
>>later, WLM will adjust the dispatching priority and the 2nd service
>>class will receive all available CPU, the first none. Needless to say,
>>my operators panicked until it was demonstrated that they were not
>>"losing time" on the production workloads.
>>
>
>This can't be right.   Adjustments to goals / DPs are made every 10 seconds.
>Could you imagine if online systems in different service classes with
>the same importance behaved this way?  For example, CICSPROD with
>IMP=2 and DB2PROD with IMP=2.
>
>Mark

Not only that, the "fair share algorithm" change to the dispatcher
in MVS/ESA V5 ensures that no address spaces at the same DP as
other address spaces will monopolize the CPU.

Mark
--
Mark Zelden
Sr. Software and Systems Architect - z/OS Team Lead
Zurich North America / Farmers Insurance Group - ZFUS G-ITO
mailto:mark.zel...@zurichna.com
z/OS Systems Programming expert at http://expertanswercenter.techtarget.com/
Mark's MVS Utilities: http://home.flash.net/~mzelden/mvsutil.html

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