| Estimating the size of Tables and Indexes(Urgent) [message #52142] |
Thu, 04 July 2002 19:34  |
siva kumar
Messages: 6
Registered: April 2002
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Junior Member |
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Hello,
Can anyone please help me in estimating the size of tables and indexes.Please say me the general procedure/existing formula for estimating the size of a table including PCTFREE,PCTUSED,INITIAL_EXTENT,NEXT_EXTENT etc with all storage parameters.
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| Re: Estimating the size of Tables and Indexes(Urgent) [message #52143 is a reply to message #52142] |
Thu, 04 July 2002 22:58  |
P
Messages: 29
Registered: May 2002
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Junior Member |
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The formula is that there is no forumla.
You need to look at you database and work it out! Know what the data is, know what tables are updated regularly etc.
As a very general rule of thumb pct free is more likely to be higher on OLTP systems. This is because of the greater propensity to have updates rows and there for migrated rows (Of course tables that are not updated will require a lower pct free). DSS systems generally do not have updates there for a low pctfree can be used. This will allow more rows to be placed into a block and benefit performance.
As for initial and next extents the sizing on these should be dependant on various things. I find that the use of locally managed tablespaces with uniform extent sizes to be the best method. As an example I have a OLTP database with large and small and medium tables. I would then have 3 different tablespace with 3 different uniform initial and next extent sizes, for example 1M 5M and 30M ...
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