Except 1MB (and a fortiori 2GB) page frames were designed to do something else: Give better TLB effectiveness - fewer entries to cover the same amount of memory.
Cheers, Martin Martin Packer, zChampion, Principal Systems Investigator, Worldwide Banking Center of Excellence, IBM +44-7802-245-584 email: martin_pac...@uk.ibm.com Twitter / Facebook IDs: MartinPacker Blog: https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker From: DASDBILL2 <dasdbi...@comcast.net> To: IBM-MAIN@listserv.ua.edu Date: 18/04/2014 20:26 Subject: Re: SORT ando MEMLIMIT best practice Sent by: IBM Mainframe Discussion List <IBM-MAIN@listserv.ua.edu> To the best of my knowledge, the answer to all your questions except the last one is "No." There are separate limits for above and below the bar storage at the address space level, but I don't know about the total system-wide use. And my answer to your last question is "Yes." With the possible exception of IBM's fairly recently added feature in which you can request virtual storage that is backed by real storage at the megabyte level instead of at the 4K byte level. This was designed to reduce paging within storage obtained above the bar. What I was really trying to imply was a rule of thumb by which we should not condemn anything before we have tried and measured it and can prove it better or worse than what we had before. Bill Fairchild ----- Original Message ----- From: "Paul Gilmartin" <paulgboul...@aim.com> To: IBM-MAIN@LISTSERV.UA.EDU Sent: Friday, April 18, 2014 2:07:29 PM Subject: Re: SORT ando MEMLIMIT best practice On Fri, 18 Apr 2014 17:54:01 +0000, DASDBILL2 <dasdbi...@comcast.net> wrote: > ... Giving a gazillion bytes above the bar to process X does not necessarily mean that process X will ruin system performance. The gazillion bytes could also have come from below the bar (for some values of gazillion). ... > Are there separate pools of real storage for above the bar and below the bar? Are there separate pools of page data sets for above the bar and below the bar? Are there separate limits for total (system-wide) virtual storage in use below the bar and above the bar? Are the costs of resources (page and segment tables and other overhead) for above the bar and below the bar different? Unless the answer to at least one of these (or any similar question) is "Yes," effect of giving a gazillion bytes is the same above the bar as below. (Or is that what you were implying.) -- gil ---------------------------------------------------------------------- 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 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 lists...@listserv.ua.edu with the message: INFO IBM-MAIN
