Thanks to all who have responded on this. I've been having 'fun' experimenting with allocating files of various sizes on a badly fragmented disk volume and at least I now understand why an 'I' command against a file shown in an ISPF 3.4 list occasionally shows such surprising values.
I don't appear to be able to make ALLOCxx settings (such as PRIM_ORG or RLSE) affect matters at all. I played around with various settings, but all to no avail, but then I spotted Paul's response where he says "...ALLOC should not step in if you have SPACE coded in your JCL...". So I removed the SPACE clause in my DD statement... and the job failed with a JCL error and messages: IEF344I jobname REQ911 REQ911 - ALLOCATION FAILED DUE TO DATA FACILITY SYSTEM ERROR IGD17045I SPACE NOT SPECIFIED FOR ALLOCATION OF DATA SET The IGD... message means that "...No space was specified on the JCL or in the data class for the allocation of the data set..." which is precisely the situation. My JCL did not feature a SPACE clause, and my SMS dataclass rule for the file in question has 'override space' set to 'N', and no 'Space' values defined. I had expected ALLOC values to be used, but that did not happen. I'm not sure where to go from here. I cannot claim to be proficient with SMS at all, so I don't really want to risk upsetting a system to works (most of the time!) Regards Sean On Mon, 4 Mar 2019 at 15:50, Vernooij, Kees (ITOP NM) - KLM < [email protected]> wrote: > There are ACS options: > ACS routines can assign a Dataclass with Space Atributes plus the option > that it will override space in JCL, even for non-SMS managed datasets. > For SMS managed datasets, the DataClass' Space Constraint Relief options > can adjust space allocations. > > Kees > > > > -----Original Message----- > > From: IBM Mainframe Discussion List [mailto:[email protected]] On > > Behalf Of Feller, Paul > > Sent: 04 March, 2019 16:40 > > To: [email protected] > > Subject: Re: Disk space allocation question [EXTERNAL] > > > > It is my understanding that the ALLOC should not step if you have SPACE > > coded in your JCL. By default you should get your space request, though > > it might be in more than one extent (up to 5). Now if you have some 3rd > > party software installed it might be stepping in to prevent the initial > > X37 abend on allocation. I don't recall if you could code something in > > the ACS routines to step in to adjust the primary allocation. > > > > Thanks.. > > > > Paul Feller > > AGT Mainframe Technical Support > > > > -----Original Message----- > > From: IBM Mainframe Discussion List [mailto:[email protected]] On > > Behalf Of Elardus Engelbrecht > > Sent: Monday, March 04, 2019 6:33 AM > > To: [email protected] > > Subject: Re: Disk space allocation question [EXTERNAL] > > > > Sean Gleann wrote: > > > > >Does z/OS / SMS have a set of default space allocation sizes and if so, > > where are they held and can I alter or control them? > > > > Look in ALLOCxx as kindly suggested by Roger Lowe. > > > > If you know what SMS routines were used, look at their definitions. > > > > > > >I have a situation where insufficient contiguous disk space results in > > the SPACE request parameters supplied for a DISP=(NEW...) file with > > values that are too low to fulfil the final requirements. > > >Example: I request SPACE=(TRK,(9000,1000)… and what I get is > > ...TRK,(7200,500), which eventually leads to a B37 abend. > > > > Please post that full B37 abend message. There may be another reason why > > you are not getting what you want. > > > > What about trying to use more than one volser for your allocation > > attempts? > > > > > > >It's that 'eventually' bit that is most disheartening. I would far > > rather have the space request completely refused along with a job abend > > rather than have the system 'try to help' me. > > > > Buy more disks... ;-) > > > > Pre-allocations may help before you actually use it, but of course, how > > do you know what size is 'correct'? > > > > Groete / Greetings > > Elardus Engelbrecht > > > > ---------------------------------------------------------------------- > > For IBM-MAIN subscribe / signoff / archive access instructions, send > > email to [email protected] with the message: INFO IBM-MAIN > > > > ---------------------------------------------------------------------- > > Please note: This message originated outside your organization. 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