Interacting with a permanent storage system from a Java application is generally left to the Java Persistence API (JPA). In this post, Carol McDonald provides a closer look at the Locking and Concurrency features new to JPA 2.0. Read Carol McDonald's post entitled 'Locking and Concurrency in Java Persistence 2.0': http://blogs.sun.com/enterprisetechtips/entry/locking_and_concurrency_in_java