There are no coding requirements for the application, When you do a QSAM OPEN for Input, the first read-ahead I/Os are scheduled by OPEN, and the application program can proceed without waiting after the OPEN at
least to the point of doing the first GET. Subsequent read-ahead I/Os can overlap with the application program processing. Similarly for QSAM output, the application program can be doing PUTs into buffers while output I/O is in progress for previously filled output buffers. The application program has little control over this, other than some DCB/DCBE parameters. Jim Mulder z/OS Diagnosis, Design, Development, Test IBM Corp. Poughkeepsie NY IBM Mainframe Discussion List <[email protected]> wrote on 02/03/2017 09:06:16 PM: > From: Jesse 1 Robinson <[email protected]> > To: [email protected] > Date: 02/04/2017 01:38 AM > Subject: Re: BSAM vs QSAM > Sent by: IBM Mainframe Discussion List <[email protected]> > > I'm bowled over by David Noon's post. I did not know that QSAM > allowed asynchronous I/O operations and have not looked into coding > requirements. > > At the same time I contend that system managed interleaving is not > the same thing. While it undoubtedly speeds up I/O for 'traditional' > QSAM, the application program remains in a WAIT during all the > background happenings and cannot independently fiddle with bits and > bytes pending I/O completion. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
