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Vern, There was a document (by Rick Turner) in the knowledge base that got passed around a while back... I think that's the one that describes this behavior. (I think you posted it...) I had to find it again... http://www-912.ibm.com/s_dir/slkbase.NSF/0/06f669c96c492f6a86256d6c0064adbe? OpenDocument Here's the bit you posted perviously: <BEGIN> There's a little-known solution - turn on commitment control. Without this, jobs can take 3-4 times as long to finish. Here's an extract from an article by Rick Turner: Commitment Control & Journaling Though most database and other write operations are asynchronous, database journal receiver write operations are usually synchronous to the issuing job. This means the job is forced to wait (in the system's disk I/O write functions) for the I/O (write) to complete before it continues processing. The SLIC Journal functions can do the journal writes asynchronously if the job uses commitment control. When commitment control is in effect, the database journal write functions know that file integrity is required only at a commit boundary and not at every record update/add/delete operation. Because of this, the database journal writes are scheduled asynchronously. When a commit boundary is reached, the database functions ensure that all pending database file I/O is complete before continuing. Lab tests show that using commitment control and journaling yields performance almost equal to not using database journaling. If you use journaling but not commitment control, a job can be three to four times slower than when you don't use journaling at all. "But this means I have to change my code!" you say. True, but the cost of the changes are minimal compared to the performance benefit. In the CL program that calls the batch program, specify the files that use commitment control and open them. Start a commit cycle in the CL program before calling the batch program. In the application program(s), change the file description to specify that commitment control is in use. Once the program returns to the CL program, end the commit cycle to force any pending file I/O to complete. <END> Eric DeLong Sally Beauty Company MIS-Project Manager (BSG) 940-297-2863 or ext. 1863 -----Original Message----- From: Vernon Hamberg [mailto:vhamberg@xxxxxxxxxxx] Sent: Thursday, February 24, 2005 6:28 AM To: Midrange Systems Technical Discussion Subject: RE: SQL performance with Local journalling I would use SETOBJACC *PURGE on the file in question between the runs. But the issue is probably high I/O - without journal caching, every (probably) change in a PF is also written to disk, using more I/O. Just turning on commitment control, I'm told, turns on some journal caching. If all you want is to improve the performance, you don't need to actually do commits/rollbacks. In this case, I think I'd set lock level to *CS, to avoid long locks - check the help for STRCMTCTL. This information is based on my recollection of what I was told by one of the folks who worked on journaling at IBM, as well as the journal cache parameter on CRTJRN. I hope my memory is good - try it out. Vern At 04:49 AM 2/24/2005, you wrote: >Hi Eric, > >that's why I got them to run it the other way round - i.e. with >journalling on first - to try and eliminate this factor. Is there >something else I should be thinking. > >Regards >Evan Harris > >At 08:55 a.m. 24/02/2005, you wrote: >>Maybe they need to purge the file from storage... >> >>When they turned journaling off and reran the query, the object was already >>paged into a storage pool, giving the illusion of exceptional performance. >> >>Use the CLRPOOL command before each run... >> >>hth, >> >>Eric DeLong -- This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list To post a message email: MIDRANGE-L@xxxxxxxxxxxx To subscribe, unsubscribe, or change list options, visit: http://lists.midrange.com/mailman/listinfo/midrange-l or email: MIDRANGE-L-request@xxxxxxxxxxxx Before posting, please take a moment to review the archives at http://archive.midrange.com/midrange-l.
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