Which of the following schedule is recoverable?
(B) R₁(A)W₁(A)R₂(A)W₂(A)C₂C₁
(D) (B)C₁R₃(B)W₃(C)C₃


Answer: (D)

Explanation: S₁ = W₁(A)W₂(B)W₂(C)C₂R₁(A)W₁(B)W₂(C)C₂C₁R₃(B)W₃(C)C₃.
S₁ is recoverable since there is only one updated read which is also after other transaction got committed.
S₂ = R₁(A)W₁(A)R₂(A)W₂(A)C₂C₁.
T₂ in S₂ is reading updated value of A from T₁ and T₁ is not committed yet, T₂ must wait to commit till T₁ is not not committed
S is a recoverable schedule but it does not avoid cascaded rollback and it is not a serial schedule also.
So, option (B) is correct.

Quiz of this Question