Which of the following statements about the Two Phase Locking (2PL) protocol is/are TRUE?

2PL permits only serializable schedules
With 2PL, a transaction always locks the data item being read or written just before every operation and always releases the lock just after the operation
With 2PL, 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
A deadlock is possible with 2PL

Correct answer: A deadlock is possible with 2PL

Solution

Deadlocks can occur in the Two Phase Locking protocol because transactions may hold locks while waiting for other locks to be released, leading to a situation where two or more transactions are waiting indefinitely for each other.

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