On 11 May 2016 at 12:05, Jesse 1 Robinson <jesse1.robin...@sce.com> wrote: > One question I have. In a previous life, we defined VIO (I believe) to device > 3314 even though we had none left on the floor. The device type was still > valid in IOGEN at that time, and I was told that device architecture was more > suitable for VIO than 3380. VIO here is currently defined to 3390. Is there > any difference?
I'm not sure about the device architecture, but the traditional reason for choosing a particular and perhaps obsolete device type for VIO was to limit the space available. This was before SMS or any other controls, and if you set up 3350 or 3380 as VIO device types, an application could easily allocate and try to fill up the entire virtual disk, with potentially disastrous results for the paging system. One trick was to specify the VIO device as 2305 (the old fixed-head disk, sometimes incorrectly called a "drum"), which was very small - 5 or 10 MB, depending on the model. The 2314 was next on the list - much bigger, but still only 30 MB or so. The 2311 or 2301 might have been an even better bet, but neither was ever supported on MVS. It may be that the "device architecture" is referring to the number of 4K pages needed to hold a track image for the device in question, with how much wastage. It's kind of the opposite calculation to what makes a good paging device, i.e. how many pages fit on a track with how much left over. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
