Optimistic concurrency control

Optimistic Concurrency (also called Optimistic Locking ) is a method to control for example in enterprise resource planning systems concurrent access by multiple users on the same record without conflict and as inconsistencies.

When Optimistic Concurrency multiple users parallel access is granted. Thus, all users are only allowed read access to display or print article information eg. If, however, an article by one of the users has changed, so getting other users who try to modify the same record almost the same time, a notification that the article has been updated. In this case the user is privileged, has first changed the record. If the user leaves the record, he is deprived of his privilege again, and a next user with write access.

In contrast, locked in the Pessimistic Concurrency ( Pessimistic Locking ) when a user's access to the data of the write and read access for all other users. It is therefore no longer possible for other users accessing or printing a record until the record is released.

Pessimistic concurrency when it is assumed that a record for (nearly) to be changed every access. The Optimistic Concurrency, however, starts from the premise that records are open primarily for read access.

The Optimistic Concurrency minimize access conflicts during operation, as only simultaneous requests for changes lead to a conflict, simultaneous read accesses are not.