The hidden parameter _FIX_CONTROL can be used to enable or disable certain bug fixes. This is often done to perform testcases or simulate scenarios and see how can affect a bug.
It is configured for a single hotfix as show below (at session level or system level). in this case (3426050) disable cartesian join on complex views, this is a very useful to reduce the use of cross join;
ALTER SESSION SET “_fix_control”=’3426050:OFF’;
It is configured for multiple hotfix as show below. In this case we include 6399597, disallow HASH GROUP BY for subquery processing and the 3426050;
ALTER SYSTEM SET “_fix_control”= ‘3426050:ON’, ‘6399597:ON’…. scope=spfile sid=’*’;
A full list of bug numbers which are controlled by fix control and theirs status can be found in the V$ views;
Because it is a hidden parameter, use of _fix_control must be authorized by MOS. In databases that we all have to make our experiments you can use it without problems.
HTH – Antonio NAVARRO