On Fri, 3 Feb 2017 16:54:57 -0600, Paul Gilmartin ([email protected]) wrote about "Re: BSAM vs QSAM" (in <[email protected]>):
> 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. This is correct for QSAM in the last 35 years or so. Older versions of OS did not offer asynchronous transfers as far as the calling application is concerned, but modern QSAM uses the application API (i.e. GET and PUT macros) as the point[s] when transfers are synchronized. Between GETs and PUTs, I/O transfers continue in the background where possible. For most applications, there is no real benefit in using BSAM. > Another concern if you need to support BPAM is that BPAM and BSAM can share > more > code than BPAM and QSAM. That's fairly marginal. Much of SAM/E is in the LPA. -- Regards, Dave [RLU #314465] *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* [email protected] (David W Noon) *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
