Question

Assume transaction A holds a shared lock R. If transaction B also requests for a shared lock on R, it will

• A. Immediately be rejected
• B. Result in a deadlock situation
• C. Immediately be rejected
• D. Be granted as soon as it is released by A

Hint:

Shared locks allow multiple transactions to read the same resource concurrently, but any exclusive lock or write operation is not allowed until all shared locks are released.

Answer 1

The Correct Option is D

- Option 1: The shared lock is not rejected as both transactions are requesting read access (shared locks), so there is no conflict.
- Option 2: There is no deadlock situation in this scenario. Deadlocks usually happen when one transaction is waiting for a resource held by another transaction in an incompatible mode (like exclusive locks).
- Option 3: Shared locks are not immediately rejected. Multiple transactions can hold shared locks on the same resource.
- Option 4: This is correct. A shared lock allows other transactions to request shared locks on the resource, and it will be granted once transaction A releases the lock.
Therefore, the correct answer is 4. Be granted as soon as it is released by A.