Entity Manager
Class OroEntityManager is used to extend some native Doctrine Entity Manager functionality. If any other modifications are required, your class should extend OroEntityManager instead of the Doctrine Entity Manager.
Additional ORM Lifecycle Events
In addition to standard Doctrine ORM Lifecycle Events, the OroEntityManager triggers new events:
preClose - The preClose event occurs when the EntityManager#close() operation is invoked, before EntityManager#clear() is invoked.