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
