Restoring Table Statistics (Doc ID 452011.1)

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In this Document

Purpose

Scope

Details

How long does Oracle retain the statistics for ?

How do I know how many days the statistics are available for ?

How do I find the statistics history for a given table ?

How do I restore the statistics ?

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APPLIES TO:

Oracle Database - Enterprise Edition - Version 10.1.0.2 and later
Oracle Database - Standard Edition - Version 10.1.0.2 and later
Oracle Database - Personal Edition - Version 10.1.0.2 and later
Information in this document applies to any platform.

PURPOSE

This document outlines the facility by which statistics may be restored following their removal. This facility is available from Orale 10g onwards.

SCOPE

Assist with restoring statistics in the event that they are overwritten.

DETAILS

Beginning with Oracle10G, when statistics are gathered for a table, the old statistics are retained so should
there be any problem with performance of queries dependent on those statistics, the old ones can be restored.

How long does Oracle retain the statistics for ?

The default period for which statistics are retained is 31 days but this can be altered with:-

- where xx is the number of days to retain them

How do I know how many days the statistics are available for ?

- will return the number of days stats are currently retained for.

- will return the date statistics have been purged up to (so only dates newer then this can possibly be restored to). Any request to restore stats from this date or older will fail with: "ORA-20006: Unable to restore statistics , statistics history not available"

How do I find the statistics history for a given table ?

Will show the times statistics were regathered for a given table.

How do I restore the statistics ?

Having decided what date you know the statistics were good for, you can use:-

ie

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