Here is an IBM presentation on how to tune z/OS and DB2 memory, including some parameters to set. http://www.mdug.org/Presentations/Large%20Memory%20DB2%20Perf%20MDUG.pdf
On Wed, Apr 12, 2017 at 2:55 PM, Art Gutowski <arthur.gutow...@gm.com> wrote: > Did someone on this thread say DB2?? > > We have been experiencing similar AUX storage creep on our DB2 systems, > particularly during LARGE reorgs (more of a gallop than a creep). Our DB2 > guys did some research, opened an ETR with IBM, and found this relic: > > Q: > "[Why was] set realstorage_management to OFF when that zPARM was introduced > in DB2 version 10? > > "Details > "IBM z/OS implemented a Storage Management Design change after DB2 v10 was > released. > "• Before the design change, DB2 used KEEPREAL(NO), virtual storage > pages were really (physically) freed, high CPU cost if YES > DISCARDDATA KEEPREAL(NO), RSM has to get LPAR level serialization to manage > those pages that are being freed immediately. That added to CPU usage and > also caused some CPU spin at the LPAR level to get that serialization -- > excerpt from PTF > > "To get around/minimize the impact of the original design shortcomings that > was introduced by IBM RSM z/OS, setting zPARM realstorage_management to OFF, > would probably have been prudent on most LPARs. HP/EDS tried to address this > new issue IBM created. > > "IBM create two PTFs and changed the way DB2 and RSM manages the page frames. > > "• After a design change (now) DB2 uses KEEPREAL(YES), storage is only > virtually freed > "If DB2 doesn't tell RSM that it doesn't need a frame, then the frame will > remain backed in real storage in some form. That causes the growth of real > storage and paging and everything that goes with using up REAL storage. > KEEPREAL(YES) allows DB2 to tell RSM that z/OS can steal the page if it needs > it, but DB2 retains ownership of the page, and it remains backed with real > storage. If z/OS needs the page, it can steal it -- excerpt from PTF > > "V10 APAR PM88804 APAR PM86862 and PM99575" > > So...perhaps check your DSNZPARM and make sure it's coded appropriately for > more modern times. FYI, we are z/OS 2.2 and DB2 11.1, NFM. We are in the > process of rolling out REALSTORAGE_MANAGEMENT=AUTO (the current IBM > recommended setting) across our enterprise. > > HTH, > Art Gutowski (with assist from Doug Drain, Steve Laufer and IBM) > General Motors, LLC > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
