On 2/05/2012 6:01 PM, Uwe Oswald wrote:
Hi Andrew,
they are old fashioned since most customers don't need them. This is nothing
you will find in a book clearly stated but that's my truth :-). Let me try to
explain why. Most customers (I do WLM optimization - and cost
reduction-projects in Germany and Switzerland) have most of their batch
workload running during night. And, most of the jobs (from the MSU consumption
perspective) are running in one Serviceclass. Hence it makes no sense to have x
periods because you have very less MSU consumption in other, higher
Serviceclasses. WLM has nothing to prioritize between several Serviceclasses. 2
Periods only make sense in TSO in my eyes for example. The same is true during
day there you have your online workload which is and should be higher
prioritized. If you Online goals are right your Batch will get less CPU or no
CPU it depends.
Hope this helps you.
Regards,
Uwe
Hi Uwe,
I suppose different sites run different types of batch work. At the
sites I have worked at, there was a significant amount of batch that ran
during the day (mostly user submitted ad-hoc stuff) as well as the
overnight batch. Maybe that is also old fashioned :-)
I had an interesting experience many years ago (pre WLM managed
initiators) when I did a WLM conversion. The site had overnight batch
which all ran in one service class. For various reasons, after the
conversion we changed that service class to have 2 periods - first
period with a response time goal, second period discretionary.
Unexpectedly, the elapsed time for the overnight batch reduced about 20%.
I don't have a good explanation. My theory is that the first period
allowed the short running jobs to finish faster, then the long running
stuff benefited from fewer context switches. Either that or there was a
big benefit from MTTW in discretionary.
SMF 113 records would have been interesting if they had existed then.
In any case I still have the feeling that batch running in a single
service class, without much competition for resources might benefit from
multiple periods. The idea is to move the short jobs through quickly,
reducing the number of jobs running simultaneously.
Regards
Andrew Rowley
--
Andrew Rowley
Black Hill Software Pty. Ltd.
Phone: +61 413 302 386
EasySMF for z/OS: Interactive SMF Reports on Your PC
http://www.smfreports.com
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