You may recall my recent issues with Oracle and predicate generation, here, here, here, and here.
We set the 10195 event for the entire instance in once case to see if it would fix our general problem without breaking everything else. Alas, the 10195 event stopped generating predicates, but changed execution plans on other queries as well. We confirmed this by turning the 10195 event off at the session level and re-executing (and reparsing) the query. As a general observation, the 10195 had a tendency to favor hash joins over everything else. Now we get to decide what is more important; performance or data integrity.