How does the two phase protocol ensure serializability in database schedules? 

 Ans:  A transaction is termed to follow the two-phase locking protocol if all locking operations precede the first unlock operation in the transaction. Such type of transaction can be divided into two phases: and expanding or growing (first) phase and a shrinking (second) phase. The two-phase locking protocol makes sure serializability in database schedules. Refer any transaction. The point in the schedule in which the transaction has obtained its final lock (the end of its growing phase) is called the lock point of the transaction. Here Now, transactions can be ordered as per to their lock points - this ordering is, actually, a serializability ordering for the transactions.