Indicate which of the following schedules are admissible (i.e., could have been produced) under a legal, two-phase-locking schedule:
S₁ = r₁(A); w₁(A); W₂(B); w₃(C); r₁(D); W₂(D)
S₂ = r₃(A); w₄(A); r₁(C); r₃(D); w₃(B); w₂(D); r₃(A); w₁(D); r₃(B); r₂(C); r₁(A)

(A) I
(B) II
(C) Both I and II
(D) Neither I nor II.


Answer: (A)

Explanation: S₁ = l₁(A)r₁(A); w₁(A);l₂(B) W₂(B);l₃(C) W₃(C);u₃l₁(D) r₁(D);u₁(D)u₁(A)l₂(D) W₂(D)u₂(B)u₂(B)
S₂ = r₃(A); w₄(A); r₁(C); r₃(D); w₃(B); w₂(D); r₃(A); w₁(D); r₃(B); r₂(C); r₁(A)
No, this schedule is not admissible (i.e., could have been produced) under a legal, two-phase-locking schedule, r₂(C) is problemetic and w₁(D) conflicts with r₂(C).
So, option (A) is correct.


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