reducing exception count and improving performance

Ajay Baghel · Posted: Tue Apr 14, 2009 8:50 pm

Hi,

We are using a KSDS dataset but it is giving us a very high exception count leading to longer runtime of the job step. The job step is executing a cobol program opening the file in I-O mode and doing only 'WRITE'.

We changed the freespace parameter to 5,5 from 1,1 and increased space allocation also. But still the job is taking longer time.

Is there any way to monitor the CI-CA split activity? Also how can we reduce the exception counts? I think reducing excepiton count will help improve run time. Will increasing BUFSPC in define cluster or AMP parameter help?

Thanks,

dbzTHEdinosauer · Posted: Tue Apr 14, 2009 8:59 pm

I realize you are very busy and do not have any time to search the forum for possible threads that are like yours.

this link:
ibmmainframes.com/viewtopic.php?t=39682&sid=0d0e014e32c1a1685173120e4acac888
is from today. there are some good comments and links to reference material that you should read.

Robert Sample · Posted: Tue Apr 14, 2009 9:18 pm

Splits don't matter enough to batch jobs to make a difference -- although they can have an impact when doing online processing. Changing BUFSP can help but may have side effects if the file is used online -- it's less effective as you have less control over how the buffers are allocated between data and index components.

Your best bet is adding AMP=('BUFND=??,BUFNI=??') to your batch job. Is your file being accessed sequentially or randomly? For sequential access, use enough data (BUFND) buffers to read a cylinder -- if you're not sure how many, run a LISTCAT and get the value from there. For random access, you need to have at least enough index (BUFNI) to read in the index tree (see the INDEX LEVELS on the LISTCAT output); adding a few won't hurt and could help.

The other thing to think about is that flat files benefit from additional buffers as well. If your COBOL program reads a flat file record then writes it to VSAM you definitely want to look at buffering for both files.

Frank Yaeger · Posted: Tue Apr 14, 2009 9:21 pm