Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!BROWNVM.BITNET!RKOGUT From: RKOGUT@BROWNVM.BITNET ("R. Kogut") Newsgroups: comp.lang.asm370 Subject: Re: CP's DASD Block I/O System Service? Message-ID: <8907131248.AA20288@jade.berkeley.edu> Date: 13 Jul 89 12:37:24 GMT Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: IBM 370 Assembly Programming Discussion List Distribution: inet Organization: The Internet Lines: 14 It's been years since I looked at this, so there may be errors here, but as you're not getting a lot of response... *BLKIO works on normal VM minidisks; R/O or R/W access is controlled by the CP directory and/or link command. Any locking protocols must be supplied by the users. The easiest way of formatting the mdisks is with CMS FORMAT -- you have a choice of 512, 1024, 2048, or 4096 byte blocks. I can't remember, but I think the label is in whatever block size you choose, not 80 bytes. In any case, the relative record order should be respected. You can't use negative offsets. *BLKIO was designed to allow SQL to run with some semblance of performance. Normally, after the disk is formatted, the RESERVE command is used to create a single mode 6 file which contains all of the blocks not used for labels or CMS file directory. The HELP file for the RESERVE command contains a good descrip- tion of the layout of the physical blocks.