Databases Illuminated, 4th Edition

11.6 Optimistic Techniques

In many environments, conflicts between transactions are relatively rare, and the extra processing required to apply locking schemes is unnecessary for most of the transactions. There is a class of techniques that reduces this overhead. Validation techniques, also called optimistic techniques, work under the assumption that conflict will normally not occur. They allow transactions to proceed as if there were no concurrency problems, but just before a transaction commits, a check is performed to determine whether a conflict has occurred. If there is a conflict, the transaction must be rolled back. Because the assumption is that conflict rarely occurs in this environment, rollback will be rare. The occasional rollback ...