Grails & Hibernate Persistence Context

Comming from PHP I had some rough time to get into such a complex persistence-framework as Hibernate is one.
Anyway, this blog-series here is def. great to read:

http://andresteingress.wordpress.com/2010/03/23/getting-the-persistence-context-picture-part-i/
http://andresteingress.wordpress.com/2010/04/08/getting-the-persistence-context-picture-part-ii/
http://andresteingress.wordpress.com/2010/04/20/getting-the-persistence-context-picture-part-iii/