Question

Consider the following two transactions:
T1: read (A); read (B); if A = 0then B: = B + 1; write (B).
T2: read (B); read (A); if B = 0 then A: = A + 1; write (A).
Let the consistency requirement be A = 0 ∨ B = 0, with A = B = 0 the initial values.
a. Show that every serial execution involving these two transactions preserves the consistency of the database.
b. Show a concurrent execution of T1 and T2 that produces a nonserializable schedule.
c. Is there a concurrent execution of T1 and T2 that produces a serializable schedule?


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  • CreatedJanuary 29, 2011
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