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Optimum Declaration for VSAM performance...!


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jones.jebaraj84

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Joined: 26 Nov 2008
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PostPosted: Fri Mar 20, 2009 12:14 am
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Hi All,

I have a KSDS VSAM file with 16 digit key and record length 17500. when i am seaching for records in this file, the job runs more than 30 mins thus giving poor performance. I tried the Buffering parameters BUFND and BUFNI and was able to reduce the job run time to 13 mins. Is there any way i can still reduce the run time.

Which could be the optimum CI SIZE and other parameters i can use to get the optimum performance...

Thanks... icon_smile.gif
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dick scherrer

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Joined: 23 Nov 2006
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PostPosted: Fri Mar 20, 2009 12:28 am
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Hello,

Quote:
when i am seaching for records in this file,
How many "hit" records are you searching for? If you are searching for a few records by key, the process should run in a few seconds.

How many records are in the file? Is it possible that your "search" must pass all of the records rather than accessing records directly?
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Robert Sample

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PostPosted: Fri Mar 20, 2009 1:14 am
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Post a LISTCAT for the file. Are you searching with a program or utility?
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jones.jebaraj84

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PostPosted: Fri Mar 20, 2009 8:58 pm
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My File has about 100 records with unique keys (16 digits). I have a main File which has about 10 million records. Each record in the Main file will have one match in my VSAM file (100 reocrds).
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Robert Sample

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PostPosted: Fri Mar 20, 2009 9:05 pm
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Your original post talks about slow search times for a VSAM file. Now you're talking about two VSAM files. Are you even sure you know what you're attempting to do? It's not clear on this end what you're asking.

And you've been asked to provide data which I'm not seeing. When you are searching, how are you searching -- language (or utility), access method, and other such information would be helpful (as in critical, as in don't give us something to understand your processing you're not likely to get any help).
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jones.jebaraj84

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Joined: 26 Nov 2008
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PostPosted: Sat Mar 21, 2009 2:56 am
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Apoligize if i am not clear on my question.

Plesae find the details as below:

Main File (Non VSAM Flat file) - 10 million records (approx)
VSAM file - 100 records approx
Language : COBOL, JCL

My program takes one record from the Main file and froms a 16 digit key. This 16 digit key from the main file is matched with the VSAM key to find for a exact match. If the match is found that particular VSAM record is processed and output is written to a flat file.

I am in the process of improving performance of this program. Now the job runs 15 mins. And this is because for every instance in the main file a VSAM search is done in the VSAM file. there are many I/O operations taking place in this process. Is there any way i could minimise the time the job runs.
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Robert Sample

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PostPosted: Sat Mar 21, 2009 3:24 am
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Load the VSAM records into a COBOL table. Use SEARCH ALL on the table. That cuts the VSAM file reads to a minimum -- once per record to load the table.
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dick scherrer

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PostPosted: Sat Mar 21, 2009 3:33 am
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Hello,

And when loading the vsam data into the cobol table/array, make sure the table is loaded in key sequence. . .
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jones.jebaraj84

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PostPosted: Mon Mar 23, 2009 10:50 pm
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Thanks a lot... icon_smile.gif
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