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Global Stats

From: Koivu, Lisa <>
Date: Tue, 28 Jan 2003 11:10:47 -0800
Message-ID: <>

Hi everyone,

Back to the lovely world of Oracle :) I've been reading up on statistics. Out of the 8.1.7 doco:
Partitioned schema objects may contain multiple sets of statistics. They can have statistics which refer to the entire schema object as a whole (global statistics), they can have statistics which refer to an individual partition, and they can have statistics which refer to an individual subpartition of a composite partitioned object.

Unless the query predicate narrows the query to a single partition, the optimizer uses the global statistics. Because most queries are not likely to be this restrictive, it is most important to have accurate global statistics. Intuitively, it may seem that generating global statistics from partition-level statistics should be straightforward; however, this is only true for some of the statistics. For example, it is very difficult to figure out the number of distinct values for a column from the number of distinct values found in each partition because of the possible overlap in values. Therefore, actually gathering global statistics with the DBMS_STATS package is highly recommended, rather than calculating them with the ANALYZE statement

The table I need to generate stats for is currently 32GB and grows by ~2GB per week. Even the smallest estimate with calculating global stats will take a long long time and I may not be able to spring for all the required temp space.

How does the list feel about global stats? Does anyone agree with the documentation that they "most important"? I'm thinking my partitioned statistics are the "most important".

Any input is appreciated. Thanks

Lisa Koivu
Oracle Database Administrator
Fairfield Resorts, Inc.
5259 Coconut Creek Parkway
Ft. Lauderdale, FL, USA 33063


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Author: Koivu, Lisa

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