Finding locked objects

Recently I was faced the following.

The tables were getting locked and the application started to hang. So I did,

      select sid from v$lock where lmode=6;

and it returned 1 row. Then I did

      select * from v$lock where sid = <sid>;

it returned 11 records and one of them was lmode 6 and reset where lmode 3.Then I did

      select * from v$locked_object where session_id = <sid>;

It returned 10 records all of them were lmode 3 and lmode 6 was missing.  So I couldn't figure out the object which was locked in lmode 6.

Then I thought it might be cascade, locking objects in the background. So I the run the following SQL to look for ON DELETE CASCADE