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which of the following is not a strict schedule?

A) R1(A),R2(A),W1(A),Abort1,W2(A),Commit2

B) R1(A),R2(A),W1(A),Commit1,W2(A),Abort2

C) R1(A),R2(A),W2(A),Commit2,W1(A),Commit1

D) R1(A),W2(A),W1(A),Commit1,W2(A),Commit2

2 Answers

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 A schedule is strict if for any two transactions T1, T2, if a write operation of T1 precedes a conflicting operation of T2 (either read or write), then the commit or abort event of T1 also precedes that conflicting operation of T2.

and for oprion D . you can see that the w2(A) precedes w1(A) without being committed or aborted.

so answer is D.

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So , always check for producer consumer situation , i.e read after write .

Ignore the initial reads , but whenever u get a producer consumer situation , check whether or not the consumer (reads or writes ) from a producer (write) only after  a commit operation.

So in option D , w1(a) is writing after w2(a) even before w2(a) has commited.Therefore option D IS correct.

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