Thanks Modic.
I got the true picture. I missed the insert part that you demonstrated.
Because you disabled Oracle from doing it the way it normaly does it with your DISABLE TABLE LOCK command. But in reality you will never use that command, would you? So would you have a locking isues if you don't have an index on that foreign key? No, of course not, if you would allow Oracle to do the things as it was deseigned for.
In an OPS environment, I used DISABLE TABLE LOCK, that's different story.

Tamil