For most installations your virtual-to-real ratio is way out of date. Cheers, Martin
Martin Packer, zChampion, Principal Systems Investigator, Worldwide Banking Center of Excellence, IBM +44-7802-245-584 email: [email protected] Twitter / Facebook IDs: MartinPacker Blog: https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker From: "Staller, Allan" <[email protected]> To: [email protected], Date: 11/09/2012 01:46 PM Subject: Re: Paging configuration recommandation on modern Dasd. Sent by: IBM Mainframe Discussion List <[email protected]> Hopefully Jim Mulder or Pete Relson can jump in if they disagree. As far as I can determine this recommendation hasn't changed much since ESA/390. I use ( REAL STOR FRAMES *3 ) for total page slots. This is per LPAR. Allocate total local paging space as (total page slots/0.35) to facilitate the block paging slot allocation algorithm. I recommend a max of 100 pps/device. (personally, I dedicate the device to paging). Spread over as many devices/paths as practical. The "optimum" VSTOR config is 2:1 virtual to real. I personally use 3:1 (RSTOR *3). This is a trade off between page rate and devices allocated. I.e. the sum of all working sets for the LPAR(in frames) is up to 3 times the number of real storage frames available. This paging rate goes up *VERY VERY* quickly after 3:1 IIRC, this is a SQUARE function. For a given original page rate: To go from 2:1 virtual/real to 3:1 virtual/real generates the ratio (9/4 * original page rate) 2.25 times To go from 2:1 virtual/real to 4:1 virtual/real generates the ratio (16/4 * original page rate) 4 times the original page rate. Additional comments interspersed below. HTH, <snip> We are implementing a DS8800 with Hyperpav and like to give ASM the best paging configuration. However, the recommendations in Initialization and Tunig Guide are outdated, speaking of 3380 devices, Seek penalties, dedicated devices, channels and control units and the Suspend/Resume logic. Occasionally PAV is mentioned, as well as z/OS 1.8, where the Suspend/Resume is no longer used, without explaining the consequences. There is no good recommendation how to set up a good paging configuration on a modern DS8800 device, nor does it explain the consequences of Hyperpav and WLMPAV set to NO in relation with OA32453 where ASM is still building a " I/O infrastructure" that utilizes Hyperpav. Nowhere is explained what this infrastructure looks like. From conversations with Greg Dyke when he was the expert in that area, I know that in the WLM managed PAV environment ASM reserved 2 access paths to each page dataset, resulting in 2n-1 aliases dedicated to a paging volume. Is this still done so in the Hyperpav situation? >>>>>As far as I know, this is still the case Our production Sysplex has 10 LCUs on the DS8800 and is connected with 8 Ficon channels. Hyperpav can select alias devices within an LCU, not over LCUs. I can allocate 10 page volumes, 1 per LCU, with 1 local page dataset per volume. This would give ASM 20 access paths to its paging configuration. I can allocate 2 page datasets on each volume, giving ASM 40 access paths to its paging configuration. Or 60 or 80. However, this all has to be handled by the 8 Ficon channels. How do I determine the optimum? >>>>> See above ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
