The problem with foreign key constraints lacking a supporting index in Oracle is not a new one. Updating a primary key (you shouldn't do that anyway) or deleting a row in the parent table needs to make sure that no entry referencing the old row is created in the child table until the transaction commits. This blog entry is about a change in Oracle 11g I stumbled upon and my script to locate foreign key constraints without an supporting index.
Tracked: Feb 10, 00:36
I just uploaded a new version of the script. Unfortunately the old script had problems identifying the correct columns when the column name of the foreign key was different from the column name of the referenced (primary) key. This should be fixed in the new version of the script.
Thanks to Gerrit for bringing the problem to my attention.