Wednesday, November 12, 2014

_optimizer_use_feedback

There is a bug in 11.2.0.2 and 11.2.0.3 that causes worse plan. need to add hint /*+OPT_PARAM('_optimizer_use_feedback','false') */ to resolve the issue.

 symptom:
first run --fast
second and onward runs --very slow
do 10046, you will see a lot of physical reads query on v$sql, you will see the plan_hash_values are different.

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