Thanks for the careful analysis, John. Very helpful. I had not thought of the option of converting to JCL SORT's using E15/E35 programs. That might actually yield potential savings, at least for programs that only use a single internal SORT request. The ones that use multiple SORT's in one program are a bit more work to break apart, and might or might not yield sufficient savings to justify the investment in re-engineering.
Peter -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of John Gilmore Sent: Monday, November 25, 2013 11:49 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Has anyone measured CPU savings using external SORT's vs internal (COBOL) SORT's? The scheme you are considering is---if I understand it---that of read prepin==>|preprocess|==>write sortin read sortin==>|external sort|==>write sortout read sortout==>|postprocess|==>write postout It involves six i/o operations per record, and it thus has little to recommend it. If instead you use Exits 15 and 35 of the external sort, either DFSORT or SYNCSORT, having the preprocessor hand unsorted records to the external sort using Exit 15 and the postprocessor take sorted records back from the external sort at Exit 35, all in one job step, you can save four of these I/O operations. This second scheme is in my experience a very muich better one than the one you are considering. It gives you all of the benefits of using the external sort and avoids gratuitous I/O. Note that the highly efficient i/o operations of SYNCSORT and DFSORT are their internal ones. They must and do use access methods to read sortin and write sortout. They do of course use these access methods more efficiently than many/most COBOL programs, but the big i/o savings are elsewhere. -- This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
