_optimizer_better_inlist_costing Tips

Oracle Database Tips by Donald BurlesonJuly 19, 2015

There are many reports of shops migrating to Oracle 11g who suddenly experience SQL slowdowns. One of the parameters that Oracle technical support is sometimes recommending is to set _optimizer_better_inlist_costing=true.

In addition to improving SQL execution time for SQL with "in" lists there are also reports that this parameter will improve SQL with outer joins.

This _optimizer_better_inlist_costing is an undocumented parameter and should only be set with the knowledge and consent of Oracle technical support.

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