Which of the following statement/s is/are correct?
I – 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_i is older than T_j), otherwise, T_i is rolled back.
II – Wait-Die It is a Non-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)

(A) Only I
(B) Only II
(C) Both I and II
(D) Both are incorrect.


Answer: (D)

Explanation: Wait-die scheme: It 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: It 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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