I seem to have missed the first part of this discussion, so this might have been mentioned, or might not be relevant.
We take hash values of all our system datasets daily for change control purposes. We use superc in batch for this (at least for PS/PDS/VSAM). It takes some time but it has worked well so far. We compare the file with itself and specify OVSUML,FILECMP Bart -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Kirk Wolf Sent: Thursday, August 20, 2015 1:46 To: [email protected] Subject: Re: Ideas for hash of a sequential data set Charles, I think that you misunderstood me. I'm suggesting that the cheap first hash (used to rule out common changes) would be over a combination of: - the first n bytes of the data set (just like you suggested) - the F1/F8 DSCB (which has stuff like DS1LSTAR and DS1TRBAL which helps to detect common changes to the end Kirk Wolf Dovetailed Technologies http://dovetail.com On Thu, Aug 20, 2015 at 12:41 PM, Charles Mills <[email protected]> wrote: > Right. That's a better idea. Seek to end minus 'n' and go from there. > > Only small negative is that if you did the first 'n' bytes and then needed > to do the whole file, you could just keep going rather than starting over. > > Charles > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of Kirk Wolf > Sent: Thursday, August 20, 2015 10:31 AM > To: [email protected] > Subject: Re: Ideas for hash of a sequential data set > > That is certainly a possibility, but wouldn't help in the (common) case of > a change that just appends to the end. Perhaps hashing both the "first n > bytes" with the F1/8 DSCB (which has information about the last TTR and > bytes in the last track) would cover more of the common changes than either > alone. > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
