Just wondering, would that be your dataset? Can it be a unix file? If so you would already have the changed timestamp.
If you are going to a checksum type of solution you could use the existing cksum unix command, something like the following worked for me: cat "//'MY.DATASET'" | cksum Regards, Leo -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Charles Mills Sent: Thursday, August 20, 2015 1:04 PM To: [email protected] Subject: Re: Ideas for hash of a sequential data set I've given a bunch of thought to this. One of the things I've thought about was storing a hash of the first 'n' bytes or records of the dataset. If that changed then you would know the dataset had changed. If it did not change then you would have to run the full dataset hash, but for some large files the savings from this two-part strategy might be significant. Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Kirk Wolf Sent: Thursday, August 20, 2015 9:55 AM To: [email protected] Subject: Ideas for hash of a sequential data set I'm trying to come up with an efficient way to see if a non-VSAM data set has been changed. Flipping the DS1IND08 bit is not an option, nor can I install SMF hooks, etc in the OS. The problem, of course, is that DSCBs don't have "last update timestamps". My initial whack at this would be to use a two-part hash: part 1: a shortened SHA1-hash of the format-1/8 DSCB part 2: a full SHA-1 hash of all of the data The goal is to calculate something when I read an entire data set and keep it, and then later I can use this to later know if I need to read the data again. So: a part 1 match is non-informative (the data set could still have changed, although not likely) a part 1 mismatch would tell me that most probably the data set has changed (or just moved?). I would then have to read the entire data set to determine if it really has changed. Thoughts? Kirk Wolf Dovetailed Technologies http://dovetail.com ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
