Oracle telephonic interview qustions

1. What is two phase commit?
2. How can you ensure the message durability in JMS topic as like in JMS queue?
3. Difference between DataSource and Drivermanger?
4. In a stateless session bean, 5 messages are posted to the JMS queue, while processing the messages if one had thrown an exception , how can you roll back the whole transaction?
5. Few questions(versioning etc...) on Optimistic concurrency control in JPA.

The above questions that i had mentioned are the typical questions that i faced.