See my answers below:
>We had a very large DFSort job that abended because of insufficient >Sortwk space with message ICE083A, indicating that 4 times 65535 tracks >were not enough. I'm guessing your system is not a z/OS 1.7 yet. Just an fyi that for systems at 1.7 or later, DFSORT allocates the sortworks as large format so they can exceed 65535 tracks (providing there are volumes with that much space available). >Looking for options to raise the default of 4 Sortwk's, I ran into 2 >questions to which I could not find the answer: >1. I cannot find any recommandations in the DFSort manuals about >the optimum number of Sortwk's. Spreading more Sortwk's about more >devices is in generally advisable, but in modern storage devices less >relevant than before. >Does DFSort really not care whether it has 5, 50 or 255 Sortwk's and how >do I determine the optimum number of Sortwk's? There's not much performance difference when you go up to say 16 or 32. However, you don't want to do something drastic like 255. The reason is that it can cause the sortworks to become fragmented and then the merge of all those strings can take longer. It's difficult to proclaim one specific number as optimal because factors like I/O contention in your environment can influence what performs best. >2. From the manual I understood that the number of Sortwk's that I >specify in the DYNALOC parameter of the ICEMAC macro's specified the >*maximum* number of Sortwk's DFSort was allowed to take and that it does >not force dymanic allocation, nor the number of Sortwk's. Tests we did >seem to show that DFSort, when it dynamically allocates Sortwk's, will >always allocate the number of Sortwk's in the ICEMAC macro. Is this >correct? DFSORT will almost always allocate the number of sortworks you specify in the DYNALOC (installation default) or DYNALLOC (runtime specified). However, if you have JCL sortworks coded but DYNAUTO=IGNWKDD is not in effect, then it will use the JCL sortworks and not perform dynamic allocation. When dynamic allocation is used, the sortwork space required is spread across all the sortworks. So more sortworks does not mean more space, but instead it means more/smaller sortwork datasets. I'm sorry if our manuals are unclear and will see if we can revise to make it more clear. I'll add that to the list of things to consider for future releases. Have a nice day, Dave Betten DFSORT Development, Performance Lead IBM Corporation email: [EMAIL PROTECTED] DFSORT/MVSontheweb at http://www.ibm.com/storage/dfsort/ ---------------------------------------------------------------------- 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
