Automating Oracle Oracle Tips by Mike Ault

Recalculation of Table Statistics

One job that can be onerous is the recalculation of the table statistics that are used by the cost based optimizer. If the statistics are not kept up to date the cost based optimizer will make bad choices as to optimization paths resulting in poor performance or even bad results. Usually tables are being analyzed either by a shotgun procedure that just analyzes all tables in the application on a periodic basis, or, on a catch as catch can basis when the Remote DBA gets a spare evening. The procedure in Figure 6 can be used to look at the gross contents of a table (based on the actual row count verses the stored row count in the Remote DBA_TABLES view) and determine if the table has changed by a specified percent, if so, it is re-analyzed. The procedure also determines from the row count data if the table is a large table and if so, uses a sampling analysis instead of a full calculation.

PROCEDURE check_tables (owner_name in varchar2) AS
--
CURSOR get_tab_count (own varchar2) IS
        SELECT table_name, nvl(num_rows,1)
        FROM Remote DBA_tables

SEE CODE DEPOT FOR FULL SCRIPTS

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