Note that my COBOL sort days are long ago so what I am saying may no longer be true. What used to happen with E35 is that SORT did NOT create the final sortout file: the program was given the sorted records from the last merge set. So you saved, at a minimum, that set of I/O. Each COBOL return from the E35 exit was really the equivalent of a write to the sortout file from the sort standpoint. If I remember correctly, there was also I/O savings using E15, but I do not remember what that savings was. Lloyd
>________________________________ > From: John Gilmore <[email protected]> >To: [email protected] >Sent: Monday, November 25, 2013 11:49 AM >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. > >John Gilmore, Ashland, MA 01721 - USA > >---------------------------------------------------------------------- >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
