Hidden Oracle Parameters

These are my notes on different (so called) hidden Oracle parameters (underscore parameters). This is definitly not a complete overview, but rather a smal summary of more or less useful parameters I´ve stumbled across. If you have experiences and knowledge that should be added, please write a comment or send me an e-mail.

_miminal_stats_aggregation
Default value: TRUE
When this parameter is set to TRUE, Oracle will minimize the aggregation operations need to be completed. One of the ways this is done, is by NOT aggregating statistics which is a result of a partition exchange (partition exchange operation), as for instance. :

ALTER TABLE test_tab EXCHANGE SUBPARTITION P_20100209_OTHERS WITH TABLE load_tab;

In this occation the statistics must be generated manually for the subpartition after the exchange is completed for the aggregation to take place.

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