Question

What is two-phase locking? How does it guarantee serializability?

Answer 1

In databases and transaction processing, two-phase locking (2PL) is a concurrency control method thatguarantees serializability. ... Expanding phase: locks are acquired and no locks are released. Shrinkingphase: locks are released and no locks are acquired.

Answer 2

In databases and transaction processing, two-phase locking (2PL) is a concurrency control method that guarantees serializability. ... The protocol utilizes locks, applied by a transaction to data, which may block (interpreted as signals to stop) other transactions from accessing the same data during the transaction's life.