Yes, and Thank you Art for that - I've passed this info on to our DB2 SYSPROG
Carmen ----- Original Message ----- From: "Art Gutowski" <arthur.gutow...@gm.com> To: IBM-MAIN@LISTSERV.UA.EDU Sent: Wednesday, April 12, 2017 2:55:53 PM Subject: Re: Paging subsystems in the era of bigass memory 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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
