Database Systems: Concepts, Design and Applications

12.6. Optimistic Methods for Concurrency Control

The optimistic method of concurrency control is based on the assumption that conflicts of database operations are rare and that it is better to let transactions run to completion and only check for conflicts before they commit. An optimistic concurrency control method is also known as validation or certification methods. No checking is done while the transaction is executing. The optimistic method does not require locking or timestamping techniques. Instead, a transaction is executed without restrictions until it is committed. In optimistic methods, each transaction moves through the following phases:

• Read phase.

• Validation or certification phase.

• Write phase.

12.6.1. Read Phase

In a Read phase, ...