Working with rollbacks in JPA

First examples you could see about JPA shows you how easy is to work with it. Don't misunderstand me, I like JPA, we (the developers) need a standard in the ORM world.
What I mean is when you really start working in a project using JPA discover you must understand fine the standard and the ORM engine implementing it (in my case TopLink).

Previously, in another post I put a couple of links on how to detach entities, here I would like to point to another post, from David Van Couvering's blog, talking about transaction rollbacks.