Something I presented recently during an Oracle Database 12c Performance Management and Tuning class. Hints are a double-edged sword; they may do more harm than good. What if hinted SQL comes from an application that you as the DBA in charge can’t modify? You can tell the Optimizer to ignore that nasty hint.
One method is to use alter session set “_optimizer_ignore_hints”=true; This will make the optimizer ignore all hints during that session – also (more...)