Mostly the same CCW opcodes. ECKD added some and a few obsolete ones are gone. Of course, FBA and FCP are new.
Physical volumes are another matter - he's dead, Jim. ________________________________________ From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of Grant Taylor <0000023065957af1-dmarc-requ...@listserv.ua.edu> Sent: Monday, July 31, 2023 10:05 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Definition of mainframe? Was: Ars Technica On 7/31/23 12:45 PM, Colin Paice wrote: > A volume is a convenient picture - they no longer exist on modern DASD. ACK My limited understanding is that the S/360 or S/370 would probably not recognize anything in use today as DASD. The S/390 /might/ see something that vaguely reminds it of DASD through ESCON / FICON. It seems as if things are significant numbers of layers of abstraction and emulation. > Data is spread across many different PC sized disks. Yep. It's amazing if not mind blowing what can be done with abstraction and virtualization of storage. > We have extended volumes which are bigger than traditional volumes. > It gives more space for the same number of volumes. :-) > A "track" is mapped to one PC sized disk, and block on disk.. > If you rewrite a track it will most probably go to a different > PC disk. In the storage controller there is a big array which has > VOLID.CYL.Track -> pcdisk.position. I'm not unpacking and scrutinizing that based on your "Some of the above is not true" comment. > I can "copy a dataset" on the same DASD subsystem just by copying > the relevant bits of this array. So if we have part of dataset1 > USER00.00.01 -> PCDISK1. 4000 the copy creates USER99.4002.12 -> > PCDISK1.4000. This copy takes a second or so. There is no data > transfer. If you update dataset1, then its VOLID.CYL.track will > point to a new block, and so the arrays diverge. This sounds like what I generally hear referred to as "copy on write" and is frequent enough that it's abbreviated as C.O.W. and multiple things support this, one even with COW in the file name. > If we copy the dataset to a different DASD subsystem - then every block > will be read - and written to the other subsystem. Yep. > Some of the above is not true - but it gives the picture. ;-) Grant. . . . ---------------------------------------------------------------------- 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
