Solution

The correct answer is 3) B and C Only.

Key Points

• Tree locking is a locking protocol used in databases to manage concurrent transactions.
• In tree locking, transactions must lock nodes in a tree structure, following a specific order to prevent circular wait conditions, which ensures freedom from deadlock (Option B).
• Tree locking allows a transaction to lock data items earlier in its execution, which helps in maintaining the required order of locking (Option C).

Additional Information

• Option A: Tree locking does not necessarily ensure shorter waiting times. Waiting times depend on various factors including the workload and the specific implementation of the locking protocol.
• Option D: Tree locking can actually ensure a greater amount of concurrency because it allows for more flexible lock acquisition compared to strict two-phase locking.