Oracle Database - _FIX_CONTROL Optimizer Parameter

_FIX_CONTROL is a special hidden parameter introduced in 10.2.0.2 which can be used to enable or disable certain bug fixes.

This is typically used in the optimizer area to allow specific fixes to be turned on or off as some fixes can have a significant effect on execution plans.

A full list of bug numbers which are controlled by fix control can be found in the V$ views:

1. V$SYSTEM_FIX_CONTROL
2. V$SESSION_FIX_CONTROL

• Alter session

ALTER session SET "_fix_control"='8855396:OFF';

• Hint:

/*+ OPT_PARAM(‘_fix_control’ ’9195582:0′) */

• Init.ora Parameter “_FIX_CONTROL”
• 11.2.0.2 performance stories