EXPMAX limit applies to total storage used by concurrent sorts. Usually when excessive paging happens it's in environments like DB2 where there's a high number of "old" frames in central storage that have not been recently referenced. DFSORT includes those frames in its calculations of storage available for memory object, Hiperspace or Dataspace sorting. The way to limit that is with the EXPOLD installation default. Usually I recommend EXPMAX be left at its shipped default of MAX but change EXPOLD from its shipped default of MAX to EXPOLD=0. This causes DFSORT to only consider available frames in its calculations and minimizes the risk causing pages to be stolen from other workloads like DB2. Usually customer is having a severe aux stor problem which is why I normally recommend going straight to EXPOLD=0 and then they can gradually increase it and monitor the effect on paging and performance.
EXPMAX, EXPOLD and EXPRES are described in more detail in Chapter 4 of the DFSORT Tuning Guide. There is a section on Hipersorting, Memory Object Sorting and Data Space Sorting which describes and gives recommenations for setting these installation default. Have a nice day, Dave Betten IBM Corporation email: [email protected] IBM Mainframe Discussion List <[email protected]> wrote on 08/05/2014 06:38:33 AM: > From: Martin Packer <[email protected]> > To: [email protected] > Date: 08/05/2014 06:38 AM > Subject: Re: Anothe DFSORT question (EXPMAX) > Sent by: IBM Mainframe Discussion List <[email protected]> > > I'm hoping my colleague Dave Betten will chime in on this at some point. > Particularly as z/OS 2.1 DFSORT has some enhancements in this area. > > CONCURRENCY is always the challenge here. And equally I would reinforce > MEMLIMIT with a decent IEFUSI exit (which I would hope included limiting > hiperspace). > > I've seen this scenario a number of times, often represented by the RMF > interval-level Minimum Available Frames being near zero while the > interval-level Average Available Frames is usually (but not always) > somewhat higher. > > Cheers, Martin > > Martin Packer, > zChampion, Principal Systems Investigator, > Worldwide Banking Center of Excellence, IBM > > +44-7802-245-584 > > email: [email protected] > > Twitter / Facebook IDs: MartinPacker > Blog: > https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker > > > > From: "R.S." <[email protected]> > To: [email protected] > Date: 05/08/2014 11:28 > Subject: Re: Anothe DFSORT question (EXPMAX) > Sent by: IBM Mainframe Discussion List <[email protected]> > > > > W dniu 2014-08-05 11:23, Elardus Engelbrecht pisze: > > Radoslaw Skorupka wrote: > > > >> EXPMAX Specifies the maximum total amount of available storage to be > used at any one time by all Hipersorting, memory object sorting, and > dataspace sorting applications. > >> Is it the limit for all concurrently running DFsort jobs/tasks or it is > per job limitation? > > Hmmm, interesting question, but see this note (DFSORT Application > Programming Guide): > > > > [snip] > > > > So, it seemed that whatever the limit is, DFSORT will check it anyways > and all jobs are checking each other's usage. If one job is hogging > storage, others will have to wait, reduce their demand or use other > storage methods. > > > > Is the question related to a problem you're having? > > > Yes. I observed excessive paging (and OLTP problems) when some DB2 REORG > job runs. REORG does use DFsort under the cover. I limited the job using > MEMLIMIT (and REGION) in a jobcard, but DFsort was smarter: instead of > 64-bit Memory Objcects it used Hiperspaces. The result was as before: > excessive paging. We talk aout tens of gigabytes used by single job. > > > Regards > > -- > Radoslaw Skorupka > Lodz, Poland > > > > > > > -- > Treść tej wiadomości może zawierać informacje prawnie chronione Banku > przeznaczone wyłącznie do użytku służbowego adresata. Odbiorcą może być > jedynie jej adresat z wyłączeniem dostępu osób trzecich. 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