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Recoverability

Consider the serializable schedule: 

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

(where the final value of Y is dependent on the X value)

Notes:

  • the final value of X is valid (change from T2 rolled back)
  • T1 reads/uses an X value that is eventually rolled-back
  • even though T2 is correctly aborted, it has produced an effect
Produces an invalid database state, even though serializable.