Which of the following option is correct regarding Wound-Wait and Wait-Die schemes?
(A) Wound-Wait is a preemptive technique for deadlock prevention. When transaction T_i requests a data item currently held by T_j, T_i is allowed to wait only if it has a timestamp smaller than that of T_j (i.e. T_j is younger than T_i), otherwise, T_i is wounded by T_j.
(B) Wait-Die is a non-preemptive technique for deadlock prevention. It is a counterpart to the wound-wait scheme. When Transaction T_i requests a data item currently held by T_j, T_i is allowed to wait only if it has a timestamp larger than that of T_j , otherwise T_j is rolled back (T_j dies ).
(C) Both (A) and (B)
(D) Neither (A) nor (B)


Answer: (D)

Explanation: Wait-die scheme is a non-preemptive technique for deadlock prevention. When transaction T_i requests a data item currently held by T_j, T_i is allowed to wait only if it has a timestamp smaller than that of T_j (That is T_i is older than T_j), otherwise T_i is rolled back (dies)

Wound-wait scheme is a preemptive technique for deadlock prevention. It is a counterpart to the wait-die scheme. When Transaction T_i requests a data item currently held by T_j, T_i is allowed to wait only if it has a timestamp larger than that of T_j, otherwise, T_j is rolled back (T_j is wounded by T_i)

So, option (D) is correct.

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