This week's book giveaway is in the Performance forum. We're giving away four copies of The Java Performance Companion and have Charlie Hunt, Monica Beckwith, Poonam Parhar, & Bengt Rutisson on-line! See this thread for details.
Regardless of the second level cache implementation you choose, the mechanisms for commiting changes to the database are the same as if you were not using it, i.e. when you commit your transaction your inserts/updates/deletes are made in the database.