The comparison of Lock-Based, Timestamp-Based, and Optimistic Concurrency Control Mechanisms are as follows:
| Feature | Lock-Based Concurrency Control (LBCC) | Timestamp-Based Concurrency Control (TBCC) | Optimistic Concurrency Control (OCC) |
|---|---|---|---|
| Approach | Uses locks to control access to resources. | Assigns timestamps to transactions and orders them. | Allows transactions to run freely and checks for conflicts at commit time. |
| Conflict Handling | Prevents conflicts by using locks (shared for reads, exclusive for writes). | Resolves conflicts based on timestamps (abort & restart if out of order). | Detects conflicts at commit time and rolls back conflicting transactions. |
| Deadlock Possibility | Yes, because transactions wait for locked resources. | No, transactions do not wait. | No, transactions do not block resources. |
| Abort Rate | Low, transactions wait instead of aborting. | High, transactions often restart if conflicts occur. | Moderate to high, depends on the frequency of conflicts. |
| System Overhead | High, due to lock management and waiting. | Moderate, requires timestamp management but no locks. | Low during execution, high at commit time due to validation. |
| Suitability | Works well in high contention environments with frequent updates. | Best for read-heavy systems with fewer conflicts. | Ideal for low-contention environments with rare conflicts. |
| Examples of Usage | Traditional databases (e.g., MySQL, PostgreSQL with strict locking). | Distributed databases (e.g., Spanner, HBase). | NoSQL databases, high-performance applications (e.g., Firebase Firestore). |