You can add KEYLEN with the length of the key (default 0) https://www.ibm.com/docs/en/zos/2.1.0?topic=kp-syntax-4 and KEYOFF with the offset of the Key (default 0).
Copies the high key value from the block into the key field of CKD then you can add skip sequential processing to Cobol, PL/I, ASM, or other languages that support keyed access programs, and full read and write programs won't be affected (beyond changing allocation at creation). You will be reading, writing existing blocks so adding or deleting records will not be possible. The elapsed time break even point is probably 5 records per cylinder average over reading all the data. All emulated 3390s read whole tracks at once. On Sat, Nov 11, 2023 at 9:35 AM Michael Oujesky <reflect...@oujesky.net> wrote: > Just a thought as I have not done it, but use BDAM to access the file? > > Michael > > At 07:59 AM 11/11/2023, David S. wrote: > > >To help resolve a question posted to a LinkedIn group I manage: > >www.linkedin.com/feed/update/urn:li:groupPost:910927-7128598004344786944 > >... I'd like to find out if there's any way to achieve *true* > >Skip-Sequential processing with a Fixed Block Sequential File with a > fairly > >short record length (i.e. DCB=(DSORG=PS,RECFM=FB,LRECL=80)? > >For example: Begin sequential processing at record number 100, *without* > >having to read the first 99 records. > >Note: We already know certain VSAM formats can do this, but the file in > >question is a DSORG=PS *Sequential* file, *not* VSAM. This is a rock-solid > >requirement and cannot be changed. We also already know how certain > >utilities such as SORT and REXX can *mimic* skip-sequential functionality > >by *discarding* unwanted records until the specified record number is > >reached. This is a likewise rock-solid requirement. Sequential processing > >*must* begin at specified starting point and there can be *no* reading of > >any records prior to that point. > >My gut feeling is it *cannot* be done - at least not with RECFM=FB. It > >*might* be possible with RECFM=F, but efficiency would then be so > >compromised it would probably outweigh any advantage from *true* > >skip-sequential processing. > > > >---------------------------------------------------------------------- > >For IBM-MAIN subscribe / signoff / archive access instructions, > >send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
