GATE | GATE CS Mock 2018 | Question 46

Assume that Ti requests a lock held by Tj. The following table summarizes the actions taken for wait-die and wound-wait scheme:
2
Fill correct status of Ti and Tj at W, Y, X, and Z respectively.
(A) Ti dies, Ti waits, Ti waits, and Tj aborts respectively.
(B) Ti dies, Ti waits, Ti waits, and Tj aborts respectively.
(C) Ti waits, Ti dies, Ti waits, and Tj aborts respectively.
(D) None of these


Answer: (B)

Explanation: 1
Wait-die scheme: It is a non-preemptive technique for deadlock prevention. When transaction Ti requests a data item currently held by Tj, Ti is allowed to wait only if it has a timestamp smaller than that of Tj (That is Ti is older than Tj), otherwise Ti 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 Ti requests a data item currently held by Tj, Ti is allowed to wait only if it has a timestamp larger than that of Tj, otherwise Tj is rolled back (Tj is wounded by Ti).
W = Ti dies, X = Ti waits, Y = Ti waits, Z = Tj aborts.
Therefore, option (B) is correct.

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