Lock Conversions Two-phase locking protocol with lock conversions: Growing Phase: can acquire a lock-S on item can acquire a lock-X on item can convert a lock-S to a lock-X(upgrade) Shrinking Phase: 。can release a lock-S 。can release a lock-X can convert a lock-X to a lock-S (downgrade) This protocol ensures serializability Database System Concepts-7th Edition 18.13 @Silberschatz,Korth and SudarshanDatabase System Concepts - 7 18.13 ©Silberschatz, Korth and Sudarshan th Edition Lock Conversions ▪ Two-phase locking protocol with lock conversions: – Growing Phase: • can acquire a lock-S on item • can acquire a lock-X on item • can convert a lock-S to a lock-X (upgrade) – Shrinking Phase: • can release a lock-S • can release a lock-X • can convert a lock-X to a lock-S (downgrade) ▪ This protocol ensures serializability