On 25 Jun 2010 15:59:23 -0700, in bit.listserv.ibm-main you wrote: >------------------------------------<snip>------------------------------------------- >My take is that most of the execution time of any given unit of work >such as a job step or CICS transaction is spent executing system code >including access methods, CICS and DB2 supplied code. An SQL statement >presumably would spend most of its time executing DB2 code. What this is >saying is that for the most part optimizing COBOL programs or REXX code >probably has relatively little payback compared to optimizations like >VSAM buffering. My take is that if a good set of guidelines is available >and used, most code and tool use will be efficient enough. >-----------------------------------<unsnip>-------------------------------------- >Clark, I'll concede PART of the validity of your point. Consider the >following example: > >Program before checks > > BEGIN LOOP. > OPEN DB FOR UPDATE. > UPDATE DB RECORD.(s) > CLOSE DB. > END LOOP. > >Run time averaged 300-330 minutes. > >Program after checks and changes: > > OPEN DB FOR UPDATE. > BEGIN LOOP. > UPDATE DB RECORD(s) > END LOOP. > CLOSE DB. > >Run time now 20-25 minutes. > >It's ok to generalize and say that most time is spent in >non-user-written code, but abuse of that code can also be incredibly >damaging. Badly written code by a shop's programming staff can lead to >terrible performance just as easily as badly written IBM or OEM code.
I saw a program with VSAM code like that. If the program had been on a critical path I would have pushed for rewriting it. Forgetting the BLOCK CONTAINS 0 clause on output non-VSAM could also do wonderful things. A good set of guidelines and minimal code review should have caught both cases. Not that I ever wrote dumb code. G D & R Clark > >This example was drawn from actual experience; I can still name the >programmer, even though he's now retired. > >Rick > ---------------------------------------------------------------------- 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
