With Hitachi DP-Vols each 7 cyl control area manages 1113 cyls of usable space per volume. The 3390-A volumes, however, do not have to be allocated in units of 1113 cyls. You can specify any custom size volume you want in cylinder units.
The 1120 cyls is allocated in 672 track pages, and the 7 cyls control area is in the first page. The control area has things like record zero, bitmaps, etc. The pages are not allocated contiguously on the media, and there can be gaps of unallocated pages if nothing is written to them. For a simple example, a 1344 track data set with 1300 unused tracks will only allocate one page, and the next data set starting on track 1345 will be on a new page. The page for track 673 to 1344 will not be used in the pool. There is a huge impact on SMS if track geometry changes, because it is used for allocation. Look at bytes/track in the Base Configuration. Ron -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Edward Gould Sent: Wednesday, January 10, 2018 9:18 AM To: [email protected] Subject: Re: [IBM-MAIN] Number of Cylinders per Volume > On Jan 10, 2018, at 5:26 AM, R.S. <[email protected]> wrote: > > W dniu 2018-01-09 o 23:59, Mike Schwab pisze: >> EAV volumes must be an exact multiple of 1,113 cylinders. Under 64K >> volumes some storage devices allow multiple of 1,113 cylinders others >> multiples of 1 cylinder. > > AFAIK it's not. > 1113 multiple is a feature of DS8k arrays. > EAV can be any number of cylinders, but EAS (the part above 65520 cyl) should be multiple of MCU (MCU=21 cyl). Radoslav: I am not sure I have heard any such promise. The only promise I have ever heard that if you are fully SMS any change in geometry would be unfelt, i.e. no JCL changes. Ed ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
