What Is The Difference Between OCC and PCC ?

Optimistic Concurrency Control (vs) Pessimistic Concurrency Control

Pessimistic Concurrency Control :

                                                    On updating the data, the record gets locked and no one else can access that record for updating. It becomes a read-only record till the lock is released. Once the lock gets released, the record can be locked again and get updated for a different user.

Optimistic Concurrency Control :
                                                    This allows multiple user to open up the same record for updation . Record gets locked only while updating the record. This is the most preferred way of locking for the web application.