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
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.