Quote Originally Posted by tamilselvan
Indexes on FK are needed otherwise you will have locking issues.
That was true for pre-9i databases and only, if you deleted a parent key (with DELETE CASCADE defined on FK) or if you updated a PK column of the parent that was referenced by child's FK.

But since 9.0, even when any of those two (rather unusual) situation occurs, Oracle doesn't need index on FK to prevent locking of child table. In short, indexes on FKs are not needed any more to prevent locking.