Example of Transaction Failure (cont)
Abort / rollback scenarios:
T1: R(X) W(X) A [1] [2] [3]
T2: R(X) W(X) C
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Case [1] is ok
- all effects of T1 vanish; final effect is simply from T2
Case [2] is problematic
- some of T1's effects persist, even though T1 aborted
Case [3] is also problematic
- T2's effects are lost, even though T2 committed
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