Checking Optimizer Compatibility

Sometime optimizer may not be compatible.  It is usually the result of an in-place upgrade or patch. The result is that the production server may behave differently from the development and test servers. 

To check the compatibility you can run below query.

set serveroutput on
DECLARE
ver VARCHAR2(30);
compat VARCHAR2(30);
BEGIN
dbms_utility.db_version(ver, compat);
dbms_output.put_line('Version: ' || ver ||' compatible: ' || compat);
END;
/
Version: 11.2.0.4.0 compatible: 11.2.0.0.0

PL/SQL procedure successfully completed.