Adding a @Version annotation to a CDT field exemplifies which type of locking?

The presence of a @Version annotation on a custom data type (CDT) field indicates the use of optimistic locking. This approach allows multiple transactions to occur simultaneously without locking the data. In optimistic locking, the assumption is made that multiple transactions can safely operate on object data without interfering with each other.

When an application attempts to save changes to an entity containing a @Version annotated field, the system checks if the version number of the object in the database matches the current version. If they match, the update proceeds, and the version number is incremented. If they do not match, it suggests another transaction has altered the data since it was read, leading to a failure of the update operation. This mechanism reduces contention and improves performance, especially in scenarios where conflicts are rare, making it well-suited for distributed systems where multiple transactions may interact.

Other locking types, such as pessimistic locking, exclusive locking, and shared locking, involve different strategies where access to the data is restricted to prevent concurrent modifications, which is not the case with optimistic locking.