Additional problems can arise when transactions abort.

Consider the following schedule where transaction T1 fails:

T1: R(X) W(X) A
T2:             R(X) W(X) C

Abort will rollback the changes to X, but ...

Consider three places where rollback might occur:

T1: R(X) W(X) A [1]     [2]        [3]
T2:                 R(X)    W(X) C