The Two-Phase Locking Protocol (Cont.) Two-phase locking does not ensure freedom from deadlocks Cascading roll-back is possible under two-phase locking.To avoid this, follow a modified protocol called strict two-phase locking.Here a transaction must hold all its exclusive locks till it commits/aborts. Rigorous two-phase locking is even stricter:here all locks are held till commit/abort.In this protocol transactions can be serialized in the order in which they commit. Database System Concepts-5th Edition,Oct 5,2006 16.9 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 5 16.9 ©Silberschatz, Korth and Sudarshan th Edition, Oct 5, 2006 The Two-Phase Locking Protocol (Cont.) Two-phase locking does not ensure freedom from deadlocks Cascading roll-back is possible under two-phase locking. To avoid this, follow a modified protocol called strict two-phase locking. Here a transaction must hold all its exclusive locks till it commits/aborts. Rigorous two-phase locking is even stricter: here all locks are held till commit/abort. In this protocol transactions can be serialized in the order in which they commit