At one time, and I don't know if it still works this way, if you allocated a temporary dataset with disp=mod,pass and didn't open it in the first step, when you opened it in the second step with disp=mod, it would read the residual data from the work disk at the point where the file was allocated. We ran into this in an ASML proc where the LINK step had garbage when the SYSLIN wasn't opened in the ASM step.
Jon L. Veilleux [EMAIL PROTECTED] (860) 636-2683 -----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Paul Gilmartin Sent: Thursday, July 06, 2006 2:40 PM To: [email protected] Subject: Re: avgrec/avgblk history ? On Thu, 6 Jul 2006 12:58:50 -0500, Ed Gould <[EMAIL PROTECTED]> wrote: > > >> The SAMe SU (IIRC) assumed that all blocks would be the same size > >> except for the last. I don't recall of finding short blocks in any > >> of the QSAM type datasets sine the SAMe came out. I don't recall of > >> a programmer ever needing a short block. While there may b e a few > >> out there I have never run across them personally. > >> > > It has long been possible to create interior short blocks by at > > least the following techniques: > > > > o RECFM=V > > > > o DISP=MOD > > > > I doubt that SAMe would have had the influence to change either of > > those. > > > > -- gil > Gil, > > WHile that is true no programmer I ever ran into, ever trusted "MOD" . > Yes it does work though. The programmers really only use of mod was > in checkpoint restart tape. Even then it was grimaced at. > Back in the "old times" uptime was at best bad (can we say 5 > minutes?) so no one really trusted it (MOD). > This is the first I have heard of unreliability of DISP=MOD. Is that the consensus of readers here? That said, my most frequent uses of MOD are for its collateral effects: o Conditionally create a data set in an IEFBR14 step with DISP=(MOD,CATLG), then write it in a subsequent step with DISP=OLD. o Conditionally delete a data set with DISP=(MOD,DELETE). o DISP=MOD,DSN=HLQ.LLQ(&MEMBER) to prevent overwriting an existing member. I've distributed some JCL using this, and about once a year I get a phone call about a Sx14 ABEND. Generally, the caller is grateful when I remind him he was about to overwrite, and renames the existing member for backup. -- gil -- StorageTek INFORMATION made POWERFUL ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html ----------------------------------------- This e-mail may contain confidential or privileged information. If you think you have received this e-mail in error, please advise the sender by reply e-mail and then delete this e-mail immediately. Thank you. Aetna ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
