Data sets on tape are created by OPEN. For that matter, allocation does no I/O for card punches, paper tape punches or printers; if you have the first two that is TMI.
-- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List <[email protected]> on behalf of David Spiegel <[email protected]> Sent: Wednesday, August 7, 2019 1:04 PM To: [email protected] Subject: Re: CPU time cost of dynamic allocation That's true for DASD, but, not for Tape, IIRC. On 2019-08-07 12:53, Seymour J Metz wrote: > They say that the memory is the second thing to go (I don't remember the > first.) IEFBR14 with DDDISP=(,PASS) or DISP=(,CATLG) does allocate a new data > set. there would be much wailing and gnashing of teeth if it stopped doing > that. > > > -- > Shmuel (Seymour J.) Metz > https://nam02.safelinks.protection.outlook.com/?url=http:%2F%2Fmason.gmu.edu%2F~smetz3&data=02%7C01%7C%7Cbf913ac8c88544d06ac908d71b57cd5c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637007936258345512&sdata=VvGKdsg2Spkk4Kq0WeVM3amVpcusMCi8yL%2BZEPkXYNw%3D&reserved=0 > > ________________________________________ > From: IBM Mainframe Discussion List <[email protected]> on behalf of > CM Poncelet <[email protected]> > Sent: Wednesday, August 7, 2019 12:34 PM > To: [email protected] > Subject: Re: CPU time cost of dynamic allocation > > >From years ago, I *think* an IEFBR14 step with DISP=(,CATLG) [or > (,PASS)] does not physically allocate a dataset on a VOLSER but only > registers it in the usercat. Have you checked whether it is in the VTOC? > > Chris Poncelet (retired sysprog) > > > > On 06/08/2019 20:38, Charles Mills wrote: >> FWIW I tried adding DISP=(,PASS) to all of the DDs and adding another (BR14 >> also) step. No difference in the step CPU time -- still 0.00 seconds. >> >> Of course, one could play guessing games all day. Is the Initiator smart >> enough to know the whole job is one big no-op? I would guess not, but who >> knows. >> >> Charles >> >> >> -----Original Message----- >> From: IBM Mainframe Discussion List [mailto:[email protected]] On >> Behalf Of Paul Gilmartin >> Sent: Tuesday, August 6, 2019 12:45 PM >> To: [email protected] >> Subject: Re: CPU time cost of dynamic allocation >> >> On Tue, 6 Aug 2019 12:25:05 -0400, Charles Mills wrote: >>> OTOH I have an IEFBR14 batch job on the same machine that allocates 15 >>> temporary datasets in JCL. The entire job lock, stock and barrel uses >>> (according to IEF032I) .00 CPU seconds. Can anyone explain why JCL >>> allocation is apparently much more CPU efficient than SVC 99 allocation? >>> >> Nowadays, z/OS performs some special optimization for IEFBR14 (it knows >> it's not going to use those data sets anyway.) Might that come into play >> here? >> >> ---------------------------------------------------------------------- >> For IBM-MAIN subscribe / signoff / archive access instructions, >> send email to [email protected] with the message: INFO IBM-MAIN >> . >> > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > . > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
