From the application program's point of view, there is no overlap. Once a read or write is issued, the TCB WAITs until the I/O is complete. Of course the application can code for subtask processing to do I/O separately from calculation, but that's a whole nother level of escalation in program complexity.
As I said before, other than POC, I can't imagine why anyone would sign on for this quagmire to save an ever diminishing thimbleful of performance. Once upon a time, machines were hugely expensive and people were a replaceable commodity. Now the proportions are reversed. Find something more useful (if not necessarily as fun) to do with your time. . . J.O.Skip Robinson Southern California Edison Company Electric Dragon Team Paddler SHARE MVS Program Co-Manager 323-715-0595 Mobile 626-543-6132 Office ⇐=== NEW [email protected] -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Paul Gilmartin Sent: Friday, February 03, 2017 2:55 PM To: [email protected] Subject: (External):Re: BSAM vs QSAM On Fri, 3 Feb 2017 14:42:24 -0500, Farley, Peter x23353 wrote: > >OTOH you don't have to wait for completion of a READ or a WRITE. You can >issue a WRITE at the end of a processing loop and then go back to process the >next record while the WRITE completes, and only CHECK the WRITE when you are >ready to issue the next WRITE. > >Similarly for READ's, issue another READ right after the start of processing >for the prior record, then CHECK the second READ when you come back to the top >of the processing loop. > Does QSAM not overlap I/O with processing? I had expected that on the first GET QSAM would issue BUFNO READs; CHECK the first and return the record for processing while the remaining BUFNO-1 READs proceeded. Another concern if you need to support BPAM is that BPAM and BSAM can share more code than BPAM and QSAM. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
