ca.portal.admin

Calculating page size for existing database

Discussion created by ca.portal.admin on May 29, 2007
Hi,

Will someone share a formula for calculating a new page size for
existing database areas?
Thanks


linda_a_jones@fanniemae.com
703 833-3178
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Re: Calculating page size for existing database
"A formula for page size ....

1) determine a cluster size (include set pointers, calc pointers VL
pointers, data length for each record in the cluster times the
number of times each record occurs in the cluster
2) divide that cluster size into each optimal page size (for your
device type) less 32 (if the page size is 5064, divide into 5032)
3) the result with the least wasted space is perhaps the best page
size depending on usage - online might be better served by smaller
page sizes; primarily batch-used areas might best be served by larger
page sizes
4) if multiple clusters fit on one page, then repeat the above
calculations accordingly



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Calculating page size for existing database
"Linda,

What you are asking about is a process called cluster analysis. There is not a simple formula, per se. You begin with a DBAN or DB-Analyzer run which gives you average and maximum set lengths. If there are cross-area owners, those sets also have to be analyzed all the way to the ""top"" owner. What you have to do is find the ""largest"" cluster stored in the area and then decide how many you would like to have fit on a page. Rule of thumb is usually to allow for 2-3. Then you look at the device you are on and find a page large enough for that, which also makes good use of the (usually simulated these days) disk geometry. This topic is covered in any good analysis and design course.

John
Date: Tue, 29 May 2007 17:18:46 -0400
From: ""Jones, Linda A"" <linda_a_jones@FANNIEMAE.COM>
Subject: Calculating page size for existing database

Hi,

Will someone share a formula for calculating a new page size for
existing database areas?=20
Thanks

linda_a_jones@fanniemae.com=20
703 833-3178
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