Lock-Based Protocols (Cont.) Example of a transaction performing locking: T2:lock-S(A); read (A); unlock(A); lock-S(B); read (B); unlock(B); display(A+B) Locking as above is not sufficient to guarantee serializability-if A and B get updated in-between the read of A and B,the displayed sum would be wrong. A locking protocol is a set of rules followed by all transactions while requesting and releasing locks.Locking protocols restrict the set of possible schedules. Database System Concepts-5th Edition,Oct 5,2006 16.5 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 5 16.5 ©Silberschatz, Korth and Sudarshan th Edition, Oct 5, 2006 Lock-Based Protocols (Cont.) Example of a transaction performing locking: T2 : lock-S(A); read (A); unlock(A); lock-S(B); read (B); unlock(B); display(A+B) Locking as above is not sufficient to guarantee serializability — if A and B get updated in-between the read of A and B, the displayed sum would be wrong. A locking protocol is a set of rules followed by all transactions while requesting and releasing locks. Locking protocols restrict the set of possible schedules