What's difference between "Optimistic" and "Pessimistic" locking?
In the pessimistic locking when user wants to update a data it locks the record and till then no one can update data. The Other user's can only view the data when there is a pessimistic locking.
In the optimistic locking many users can open the same record for updating,and hence increases maximum concurrency. The Record is only locked when updating the record. This is the most preferred way of locking practically. In today's time the browser based application is very common and having the pessimistic locking is not a practical solution.