Deadlocks (Cont.) The potential for deadlock exists in most locking protocols. Deadlocks are a necessary evil. When a deadlock occurs there is a possibility of cascading roll- backs. Cascading roll-back is possible under two-phase locking.To avoid this,follow a modified protocol called strict two-phase locking--a transaction must hold all its exclusive locks till it commits/aborts. Rigorous two-phase locking is even stricter.Here,al/locks are held till commit/abort.In this protocol transactions can be serialized in the order in which they commit Database System Concepts-6th Edition 15.13 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 6 15.13 ©Silberschatz, Korth and Sudarshan th Edition Deadlocks (Cont.) The potential for deadlock exists in most locking protocols. Deadlocks are a necessary evil. When a deadlock occurs there is a possibility of cascading roll￾backs. Cascading roll-back is possible under two-phase locking. To avoid this, follow a modified protocol called strict two-phase locking -- 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