Oracle Riddles: Now that is interesting.
A process can prevent me from staking the claim for another. Users sometimes need me to know if they can secure a spot where another process may have been before. Needless to say, I am a pretty big deal, and users are very interested in me. However, when some stop by for a visit they often feel I haven't cleaned up very well. Do you know what I am?
posted by Eric S. Emrick at 3/28/2006
6 Comments:
the oracle process monitor (pmon) ?
Any other guesses ;-) ?
I'll bite - The transaction table in the rollback segment header block.
A row level lock, I think.
Actually, I would revise my guess to be Interested Transaction List.
Steve,
"Interested Transaction List" is indeed the answer I was looking for. Nice job. I thought the title "Now that is interesting" in conjunction with "users are very interested in my" and "I haven't cleaned up very well" would have given it away. Users will sometimes, but not always, need the ITL of a block to determine if they can lock a row. Sometimes the row is not locked. Sometimes the row lock byte indicates the row is "locked" when in fact it is not. So, we need the ITL entry for that row to get the transaction status stored in the undo segment header to determine if the row can be locked. Anyway, partial credit to Mike Wielonski is granted, given the somewhat ambiguous language used. Thanks for playing!
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