GATE | Sudo GATE 2020 Mock I (27 December 2019) | Question 18

Consider the following two statements about database transaction schedules:

I. Timestamp protocol ensures freedom from deadlock as no transaction ever waits, but the schedule may not be cascade free, and may not even be recoverable.
II. Timestamp-ordering concurrency control protocol with Thomas’ Write Rule can generate view serializable schedules that are not conflict serializable.
III. Binary Locking does not guarantee Serializability.

Which of the above statements is/are TRUE?
(A) Only I and II
(B) Only I and III
(C) Only II and III
(D) All I, II and III


Answer: (D)

Explanation: Timestamp protocol ensures freedom from deadlock as no transaction ever waits, but the schedule may not be cascade free, and may not even be recoverable.
So, statement (I) is correct.

Timestamp-ordering concurrency control protocol with Thomas’ Write Rule can generate view serializable schedules that are not conflict serializable.
Statement (II) is correct.

Binary Locking does not guarantee Serializability.
Statement (III) is also correct.

Option (D) is true.

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