As you know Oracle Data Guard provides high availability, data protection, and disaster recovery. It provides a comprehensive set of services that create, maintain, manage, and monitor one or more standby databases.
If you begin working with Data Guard and you want to learn quickly, I would like to mention a book around this area that I just finished to review:
Oracle Data Guard 11gR2 Administration Beginner’s Guide
This book has been written by Emre Baransel and Nassyam Basha.
From my point of view this is a very good book to start around this subject. It is easy to read and provides also useful real-word practices and issues.
Book Contents:
Preface Chapter
1: Getting Started Chapter
2: Configuring the Oracle Data Guard Physical Standby Database Chapter
3: Configuring Oracle Data Guard Logical Standby Database Chapter
4: Oracle Data Guard Broker Chapter
5: Data Guard Protection Modes Chapter
6: Data Guard Role Transitions Chapter
7: Active Data Guard, Snapshot Standby, and Advanced Techniques Chapter
8: Integrating Data Guard with the Complete Oracle Environment Chapter
9: Data Guard Configuration Patching Chapter
10: Common Data Guard Issues Chapter
11: Data Guard Best Practices Pop Quiz Answers
You can find some sample chapters here or the whole book here.
bdt's blog 
Hello Bertrand,
thanks for this review. From my experience, both Data Guard and Active Data Guard are elegant and relatively simple tools, yet their benefits sometimes are not well understood by the business community.
Olga
PS Liked your R scripts, too. Interesting way to present data using R – and why not?