On Sat, 11 Nov 2023 08:59:07 -0500, David S. wrote:
...
. Sequential processing
*must* begin at specified starting point and there can be *no* reading of any records prior to that point.
That sounds absurd. So if a block contains 10 records, you want to be able to read the last 5 with "*no* reading of" the first 5!? DASD don't work that way.
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.
How about UNIX files with RECFM=FB,FILEDATA=BINARY and using seek()? (But that still reads entire blocks into a buffer.) -- gil
