Db2 virtual storage is a long and complicated story but DBM1 is far and away the biggest consumer - so I think separation of functions is a more likely story than just virtual storage constraint relief (VSCR).
Cheers, Martin Martin Packer, zChampion, Principal Systems Investigator, Worldwide Cloud & Systems Performance, IBM +44-7802-245-584 email: martin_pac...@uk.ibm.com Twitter / Facebook IDs: MartinPacker Blog: https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker Podcast Series (With Marna Walle): https://developer.ibm.com/tv/mpt/ or https://itunes.apple.com/gb/podcast/mainframe-performance-topics/id1127943573?mt=2 From: Mohammad Khan <mkkha...@hotmail.com> To: IBM-MAIN@LISTSERV.UA.EDU Date: 02/11/2017 13:37 Subject: Re: Db2! was: NODE.js for z/OS Sent by: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Thu, 2 Nov 2017 20:30:21 +1100, Wayne Bickerdike <wayn...@gmail.com> wrote: <snip> > >Why DB2 has so many address spaces is probably because of the IMS heritage. >Other (simpler but equally effective DBMS) manage on a single address >space....I wish... > I believe this was due to the size limitation of 31-bit address space and unsatiable hunger of db2 buffer pool manager for which no amount was ( is ! ) enough. In theory 1.6GB ( out of a total of 2GB ) could be allocated to buffer pools and there was still use for hyperspace buffering. In fact buffer pools in dataspaces was tried at one time but all that came to and end with advent of 64-bit addressing. I'd think that locking and logging, frequent as they are, would have saved some cycles if they were local calls instead of cross memory but there simply was no room for them in DBM1. In today's world space considerations may not matter as much but the benefits of isolating these functions still remain. On the other hand I have no idea why IRLM has to be its own subsystem. Mohammad ---------------------------------------------------------------------- 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
