Hi:
We've done a couple of PoC on Hibernate and are convinced of it's power. However, we wanted to better understand how Caching works in Hibernate before going ahead in utilizing it for our project.

Let's say we have 100 Million Records in the database and we have 250 concurrent users firing different queries.

Our questions are the following:
1.) Does Hibernate cache all the 100 Million records in memory
2.) If it doesn't put all the records in memory than how does it implement caching
3.) If it does cache the entire 100 Million records than what is the sort of hardware/system configuration we are looking at?
4.) If there is a change in the Db after the first caching - how does Hibernate synchronize its' existing cache with the Db?
5.) Can this synchroization be controlled by some parameter settings and if so where would these need to be done?

An early response would be appreciated.

Thanks.

These questions are too generic. Please consider reading the book "Hibernate in Action", the early access is linked on the left side on http://www.hibernate.org/.