how to improve the performance for writing records to vsam



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how to improve the performance for writing records to vsam

Postby gopal_NKP » Wed Mar 16, 2011 11:57 am

hi,

i have a requirement as follows
one is input file. this is sequnetial.

one is output file . this is VSAM.

records are read and manipulated and then will be written to VSAM.
input records are around 6lakhs. all these records will be written to OUTPUT VSAM file.

it is taking around 22 minutes to run. how can i decrease this time. please tell me.

quick useful reply helps me alot.

thanks
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Re: how to improve the performance for writing records to vsam

 

Re: how to improve the performance for writing records to vs

Postby enrico-sorichetti » Wed Mar 16, 2011 12:03 pm

quick useful reply helps me alot.

we do useful, but we do not quick! :evil:
You should accept that on a forum people reply if and when they feel like!

post evidence that You have performance issues,
the elapsed time is a meaningless indicator,
is influenced by the system load, priority/wlm settings, and, and, ...

the way You posted the issue is just whining!
cheers
enrico
When I tell somebody to RTFM or STFW I usually have the page open in another tab/window of my browser,
so that I am sure that the information requested can be reached with a very small effort
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Re: how to improve the performance for writing records to vs

Postby NicC » Wed Mar 16, 2011 4:52 pm

'lakh' is not a mainframe term. To help others please use the correct terminology - 600,000 or 600k I think is what you mean.
The problem I have is that people can explain things quickly but I can only comprehend slowly.
Regards
Nic
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Re: how to improve the performance for writing records to vs

Postby BillyBoyo » Wed Mar 16, 2011 5:17 pm

Hard to start without knowing what type of VSAM file. A KSDS with four alternate keys is one thing. An ESDS another... An RRDS a third... For a quick response full of details, try IDCAMS and the manuals. Do the IDCAMS before and after running (or delete/define if you like and IDCAMS after run), so that you can see what affect your run has had on the file(s). Number of IOs, extents, splits where applicable, etc. If 22 minutes is a problem, will it be the same problem anyway at production priorities? As has been said, your elapsed time is dependent more on machine load. Run it on an empty machine, and it will be much quicker.
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Re: how to improve the performance for writing records to vs

Postby Robert Sample » Wed Mar 16, 2011 5:22 pm

When you say "VSAM file", do you mean KSDS or RRDS or ESDS or linear data set?
Is the VSAM file deleted and defined before the program runs?
What is the VSAM record length (average and maximum if variable)?
How many buffers (buffer space) are you using in our JCL / VSAM definition for the VSAM file?
How many buffers are you using for your input file?
Are you getting many CI or CA splits (assuming KSDS)?
Does your site use an I/O improvement tool?
What is the CPU utilization when your job is running?
What is the channel utilization for the input file and VSAM file channels when your job is running?

As was previously noted, at this point you believe you have a performance problem but there's absolutely no indication of it. Without answering questions like these, a professional cannot say for sure that there is a performance issue.
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