Difference between OCC and PCC

( OCC: - Optimistic Concurrency Control ) :- Optimistic Concurrency Control (OCC) helps increase database performance, Optimistic Concurrency only locks records from the time when the actual update is performed
OCC Enabled: Yes


PCC: - 
           Pessimistic Concurrency Control locks records as soon as they are fetched from the database for an update. Pessimistic concurrency was the only option available in Microsoft Axapta 3.0 (now a part of Microsoft Dynamics).