Limits and Statistics

Discussion created by ca.portal.admin on Jun 19, 2008
Hello Listers,
At our site we are looking at ways to reduce the CPU usage of the IDMS
CV's. I remember seeing some statistics stating that having statistics
collection on added approximately 8 - 10% CPU overhead. Also, turning on
LIMITS increased the CPU usage roughly 7%. I have found some internal
documentation that states this, but I cannot find any 'official' CA
documentation that does.=20

Does anyone else on the list remember seeing similar statements about
the CPU overhead of LIMITS & STATS?

The reason for the question is that I ran some tests on one of our CV's.
Using a testing tool we ran almost 70,000 tasks thru the CV with LIMITS
enabled and STATISTICS collection on. We then shutdown the CV and
recorded the # of tasks, CPU used, etc. Next we changed the SYSGEN to
set LIMITS disabled and STATISTICS off. We also changed the #PMOPT macro
to stop writing SMF data. We reran the exact same set of scripts. The
results showed only a 2% reduction in CPU usage.

Does this figure surprise anyone else? Any ideas what I could be missing
to only see this small reduction?

Thanks for any help you can give.

Dan Hall
GE Capital Solutions
Database Administrator

T 513.217.5060

Middletown, OH 45042
General Electric Capital Corporation
IDMS Public Discussion Forum


Re: Limits and Statistics

If you're using ADSO, you can reduce CPU by removing retrieval locks wher=
e they're not needed. If you have dialogs that are used allot during the =
day, are mostly retrieval and do only a small amount of updating, you can=
put the updating functions in a mapless dialog, do a 'LINK NOSAVE' from =
the retrieval dialog to the update dialog, have the update dialog re-esta=
blish currency and turn retrieval locks off in the retrieval only dialogs=
. If a dialog is retrieval only and does not pass currencies to an update=
dialog, the retrieval locks should be turned off. This could save allot =
of CPU and also reduce deadlocking depending on how the dialogs are coded=
and the number of transactions they process.