Small track sizes were considered more efficient for VIO because of the number of page slots that had to be used in order to satisfy the allocation. Also VIO would get all 16 extents at once, so saying TRK(1,1) was not better than saying TRK(16). When a job did the VIO allocation, it got the page slots.
In 1990 or 1991 (before I worked for Sterling Software and now CA) my employer had a series of system slowdowns which were caused by paging slot shortages, or exhaustion. We found that many jobs were using VIO for SORTWKnn DDs. This all traced back to an individual application programmer who knew just enough about VIO to see it was virtual, but did not grasp the difference between "virtual" and "unlimited". I don't remember there being a way to put a hard limit on the total amount of VIO in use by the system. Now in the days of cached and solid state DASD the I/O performance payback isn't as big. As in the previous response, the system did not set aside an entire 2314 (or 3330) worth of page slots to back the VIO requests. It just fulfilled the requests for "tracks" as they came in. Bob Longabaugh CA Technologies Storage Management -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Martin Packer Sent: Thursday, May 19, 2016 3:56 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: What was a 3314? (was: Whither VIO) The whole disk is NOT in your virtual storage; The track window IS (IIRC). Cheers, Martin Sent from my iPad > On 19 May 2016, at 21:45, Tony Harminc <t...@harminc.net> wrote: > >> On 19 May 2016 at 01:44, Martin Packer <martin_pac...@uk.ibm.com> wrote: >> It's sort of come back to me: >> >> A small track size limits the virtual storage window (probably >> usually below the line in 1989 when I looked at this). Or it might've >> been cylinder. But I think it was track. >> >> I'm wondering if anyone else remembers something like this. > > I'm not sure I get the "virtual storage window" idea. VIO emulates an > entire disk drive in virtual storage. So where is there a window? The > whole disk has to be in virtual storage at once. Well, I suppose there > could be logic to not allocate Virtual until used, but that would > surely better be left to VSM's and RSM's expertise at managaing their > respective kinds of storage. > > Now maybe VIO was changed much later (surely there wasn't expanded > storage in 1989...?) to use or perhaps favour expanded storage, in > which case a window model could make some sense. But only if VIO was > directly dealing with expanded storage rather than just requesting > that RSM use it to back virtual storage used to hold the VIO disk > data. > > Tony H. > > ---------------------------------------------------------------------- > 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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
