With EXCP, I think you'd at least have to have multiple DCBs open for the data set. I suspect that's the only way you'll be able to get multiple channel programs queued to the UCB at once. Then, IOS *might* redirect some of them to PAV UCBs so as to parallelize the I/O, but you have no direct control over that process.
At 04:03 AM 12/17/2007, Tom Quarendon wrote: >Since I got such a good response from the last question, here's another. > >My understanding of channel program execution is that there is one queue per >UCB, i.e per volume. In other words there isn't a huge amount to be gained by >executing lots of concurent channel programs to the same file (you'd get some >advantage, maybe, in that you'd be able to construct your next EXCP invocation >and have the EXCP do all the prep work for it before actually checking that >you previous one is done). >Parallel access volumes however mean that there are potentially multiple UCBs >per device and therefore multiple channel program queues. However if I examine >the list of UCB associated with the extents of my file they are all the same. >So is(are) parallel access volume technology something I can exploit in my >application? The best I could presumably do is to allow multiple channel >programs to be scheduled by my application against different extents in the >file, but since my UCB addresses are all the same, that's not going to work. >Is this an MVS configuration issue? i.e is there something that would need to >be set up on the machine to allow this? Or is this more a case of different >jobs will get different UCB addresses for the same volume, so they can be >parallelized, but you can't exploit that within a single app? >Searching on the web, Syncsort reckons it exploits PAV to get 30 percent >improvement in elapsed time or something. I want a piece of that if I can get >it. ================================================== Art Celestini Celestini Development Services Phone: 201-670-1674 Wyckoff, NJ ============= http://celestini.com ============= Mail sent to the "From" address used in this post will be rejected by our server. Please send off- list email to: ibmmain<at-sign>celestini<dot>com. ================================================== ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
