From days of yore, IBM has generally recommended 2:1 virtual to real storage. I have pushed this to 3:1 without major issues. The paging subsystem should be configured accordingly page slots approx. 3x available real.
If you are actually going to be doing serious paging, (> +/- 20 pps) the local page datasets should not be more that 30% utilized, so 9x real page slots is appropriate. Again, from days of yore, Paging seems to follow an inverse SQRT function. If the original paging rate is x, doubling the real memory available will result in a new paging rate of about (x*1)/1.4 or about 0.7 x. Tripling the read storage will result in X(/1.7) or about 0.6x HTH, -----Original Message----- From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of Charles Mills Sent: Sunday, November 3, 2019 8:17 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: How display level of paging? "Large memory" is not the situation I am dealing with. It is a modern system but it is at a service bureau and there is a substantial charge associated with real memory. My management does not want to just throw money at the system; he wants some way of seeing whether real memory constraint is a problem and whether additional real memory improves the problem. "Performance" is hard to measure because the workload is extremely varied and not directly under our control, so mostly what we have is subjective: "it's really slow today." Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Scott Chapman Sent: Sunday, November 3, 2019 5:08 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: How display level of paging? I'm not so sure that's practical and necessary for the large memory systems that we have today. Last time I looked across a number of customers it was fairly common for LPARs with hundreds of GB of memory to have paging space < 1x memory. Sometimes much less. Those with Storage Class Memory were more likely to have paging space >= real storage. But even there, we've seen >1TB LPARs with with only a few hundred GB of paging space, including SCM. Of course it is also fairly common for those large memory systems to be running with large amounts of that memory being available. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ::DISCLAIMER:: ________________________________ The contents of this e-mail and any attachment(s) are confidential and intended for the named recipient(s) only. E-mail transmission is not guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or may contain viruses in transmission. The e mail and its contents (with or without referred errors) shall therefore not attach any liability on the originator or HCL or its affiliates. Views or opinions, if any, presented in this email are solely those of the author and may not necessarily reflect the views or opinions of HCL or its affiliates. Any form of reproduction, dissemination, copying, disclosure, modification, distribution and / or publication of this message without the prior written consent of authorized representative of HCL is strictly prohibited. If you have received this email in error please delete it and notify the sender immediately. Before opening any email and/or attachments, please check them for viruses and other defects. ________________________________ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
