Database Reference
In-Depth Information
Summary
This chapter covered a lot of material that, at times, may have made you scratch your head. While locking is rather
straightforward, some of its side effects are not. However, it is vital that you understand these issues. For example,
if you were not aware of the table lock Oracle uses to enforce a foreign key relationship when the foreign key is not
indexed, then your application would suffer from poor performance. If you did not understand how to review the
data dictionary to see who was locking whom, you might never figure that one out. You would just assume that the
database hangs sometimes. I sometimes wish I had a dollar for every time I was able to solve the insolvable hanging
issue by simply running the query to detect unindexed foreign keys and suggesting that we index the one causing the
problem. I would be very rich.
