Should have mentioned, that is a thought we've considered. And we may end up doing. Just wanted a better way, if there is one. Frank
>________________________________ > From: Fred Hoffman <[email protected]> >To: [email protected] >Sent: Tuesday, April 3, 2012 3:34 PM >Subject: Re: VSAM help wanted for random reads > >Run the 4's then run the 5's. It can't be that simple. > >-----Original Message----- >From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of >Frank Swarbrick >Sent: Tuesday, April 03, 2012 4:24 PM >To: [email protected] >Subject: VSAM help wanted for random reads > >Current program does the following (in COBOL!). > >- Opens KSDS for I-O >- Sequentially processes another file (non-VSAM). >- For each record in the non-VSAM file it attempts a random (keyed) read of a >record on the KSDS file. The key is, essentially, a concatenation of a record >type code ('4' or '5') and an account number. If no record of type '4' is >found then it tries again for the same account, but with record type '5'. If >either the '4' or '5' type is found it updates it and rewrites the record >(assuming the data changed). > >This takes about 16 minutes to run. However if the 'type 5' logic is removed, >so that it only ever looks for type '4' records, it takes only about one >minute. > >Our resident VSAM expert says it has something to do with the VSAM "sequence >set" and the fact that only one is kept in memory at a time. Since the same >sequence set doesn't appear to be able to be used for both the 'type 4' >records and the 'type 5' records it's constantly going back and forth, loading >the "other" sequence set from disk. He says on VSE (which we were up until >May 2010) more than one sequence set can be in memory, but with MVS this >appears to not be the case. > > >Hopefully that reason is accurate. Is there a solution? We thought about >having two COBOL FDs pointing to two DDs, where both DDs pointed to the same >KSDS. This would probably(?) work, except for the fact of the update. > >Thanks, >Frank > > >---------------------------------------------------------------------- >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
