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Oracle 9i concurrent transaction / isolation levels

 
Nevin Anderson
Greenhorn
Posts: 1
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Hi,
I'm trying to complete an assignment regarding Oracle, and am finding my lecture notes too vague! I'm a student, so of course I have only 12 hours left to complete this or...
Given that in each case the transactions are still in progress - can someone tell me:
(a) At 1:03PM transaction A updates row R1 of table T.
At 1:04PM transaction B updates row R1 of table T.
What happens, and why?
(I think that - B will be unable to update R1 because A�s transaction has placed a lock on R. Default level read committed will allow B to read committed transactions, but nothing else until A�s transaction completes).
(b) Transactions A and B are both isolation level serializable.
At 11:43AM transaction A updates row R2 of table T.
At 11:44AM transaction B selects row R2 of table T.
What happens, and why?
(I think that - B will see R2, but be unable to do anything else until A commits)
(c) Transactions A and B are both isolation level read committed.
At 2:15PM transaction A updates row R3 of table T.
At 2:15PM transaction B updates row R4 of table U.
At 2:16PM transaction A updates row R4 of table U.
At 2:17PM transaction B updates row R3 of table T.
What happens, and why?
(I know that - this is a deadlock, neither A nor B can move... I think that Oracle will kill off A's 2:16 transaction, but not sure whether the the 2:15 will be killed off, as the deadlock would still exist)
Anybody in a sympathetic frame of mind who can help?
Cheers, Nevin.
 
It is sorta covered in the JavaRanch Style Guide.
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