GATE CSE 2024 | Set 2 | Question: 17

Question

​​​​Which of the following statements about the Two Phase Locking ($2 \mathrm{PL}$) protocol is/are TRUE?

• A. $2 \mathrm{PL}$ permits only serializable schedules
• B. With $2 \mathrm{PL}$, a transaction always locks the data item being read or written just before every operation and always releases the lock just after the operation
• C. With $2 \mathrm{PL}$, once a lock is released on any data item inside a transaction, no more locks on any data item can be obtained inside that transaction
• D. A deadlock is possible with $2 \mathrm{PL}$

Comments

Video Explanation: 2PL (Two Phase Locking Protocol)

Answer 1

Answer A,C,D

A. 2PL -> serial schedule

C. Also it's the property of 2pl which states that once a lock is relased no further lock can be taken as the shrinking phase of the transaction starts and you can't acquire any lock in the shrinking phase of a transaction.

D. Deadlock can occur in 2PL as in a schedule 2 transaction can wait for each other to release the locks. This is the disadvantage of normal 2PL