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KSDS VSAM define tune

 
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rally

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Joined: 28 Jul 2005
Posts: 37

PostPosted: Sun Feb 11, 2007 10:10 am    Post subject: KSDS VSAM define tune
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Hi,

I have a large VSAM file need reorg, below is some info for it:

1. there are many CA/CI split during online.

2. the reason to create the CA/CI is most of the new records(50%)
will be insert into last part of the file, and other 50% records will be
added to the whole file randomly.

Any idear regarding above case?

How can I overcome the CA/CI splits issue,
this make the our online transaction process came to very slow.

From normally 4 txns/second down to 1 txn/5 seconds.

Thanks.
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William Thompson

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Joined: 18 Nov 2006
Posts: 3158
Location: Tucson AZ

PostPosted: Sun Feb 11, 2007 3:19 pm    Post subject:
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Without good information, it is going to be hard.
The 50% at the rear should take care if itself but the random adds need to be addressed. The CI splits are minor, it is the CA splits that cost. What is the current CI and CA freespace? How often is the file reorged? What is the current CI and CA size?
My approach would be to start with a large CA size (full cylinder), a slightly larger than normal CI size and, maybe, 25% freespace in both and do a listcat every day looking for splits. At this point, CI splits are good and a small count of CA splits aren't too bad - while a CA split is expensive to run time, once done there is a lot of freespace now available. Keep watching and adjusting the freespace each time you reorg and you can find an optimum percentages for both CI and CA.
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Bitneuker

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Joined: 07 Nov 2005
Posts: 1105
Location: The Netherlands at Hole 19

PostPosted: Mon Feb 12, 2007 7:06 pm    Post subject:
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Also consider the index and not just data.
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William Thompson

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Joined: 18 Nov 2006
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Location: Tucson AZ

PostPosted: Mon Feb 12, 2007 7:15 pm    Post subject:
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IIRC, lately a lot of the tune-ability for indexes has been removed in favor of AMS deciding on its own. But you are right, you could really screw performance by undersizing index CIs......
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Bitneuker

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Joined: 07 Nov 2005
Posts: 1105
Location: The Netherlands at Hole 19

PostPosted: Mon Feb 12, 2007 7:18 pm    Post subject:
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