Interested Transaction List is the method through which Oracle keeps track of which transaction has updated which row in a block. I wrote an article about it a while back where I show how the ITL works and how it impacts performance in certain situations. The basis of the article is a page locking scenario I encountered. Sure, page locking is not possible in Oracle, but an ITL wait is very similar to a page lock. 

You find the article here. In Swedish here.

Please post comments and questions here.

2 Comments

  1. First off – great article.
    I am a very junior Oracle DBA and wondered how do you run the 3 statements from 3 sessions simultaneously?

  2. I’m happy you’re enjoying the article.
    With simultaneous execution of the statements, I only meant that you should have three separate sessions open at the same time. Thus it is not a timing issue as the first statement could be executed day one, then second on day two and the third on day three as long as the previous sessions/transactions are still active.
    As long as all three updates are in active sessions (that is can be committed or rolled back) at the same time, the effect will be triggered.

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