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Serializability

Consider two schedules S1 and S2 produced by
  • executing the same set of transactions T1..Tn concurrently
  • but with a non-serial interleaving of R/W operations
S1 and S2 are equivalent if StateAfter(S1)  =  StateAfter(S2)
  • i.e. final state yielded by S1 is same as final state yielded by S2
S is a serializable schedule (for a set of concurrent tx's T1 ..Tn) if
  • S is equivalent to some serial schedule Ss of T1 ..Tn
Under these circumstances, consistency is guaranteed
(assuming no aborted transactions and no system failures)