Consider the following two statements about database transaction schedules

Q. Consider the following two statements about database transaction schedules:

1. Strict two-phase locking protocol generates conflict serializable schedules that are also recoverable.
2. Timestamp-ordering concurrency control protocol with Thomas’ Write Rule can generate view serializable schedules that are not conflict serializable.

Which of the above statements is/are TRUE?

(A) I only

(B) II only

(C) Both I and II

(D) Neither I nor II

Ans: Both I and II

Solution:

Strict 2PL allows only schedules whose precedence graph is acyclic i.e. schedule is Conflict Serial. In 2PL, transactions do not release exclusive locks until the transaction has committed or aborted i.e. schedule is recoverable. Time stamp ordering schedule with Thomas write rule generate View serial schedule with BLIND WRITE. Because of BLIND WRITE it won’t be Conflict Serial.