Here you read posts on the basics this week. For more advanced tricks you will find that Ludo wrote a couple of interesting entries on setting up multi-master replication using command-line tools, and on enabling the change log when using only one server.
Replication is what many see as the killer feature of OpenDJ. Multi-master replication means you can build directory services that stay on always, tolerating crashes on individual servers, network outages, even loss of data center while continuing to serve directory data for client applications that perform both reads and writes. The model is based on the idea of loose consistency with built-in conflict resolution. While you can configure replication in the Quick Setup wizard, there are times when you want to be able to script the configuration, or change it after installation. Read Ludo’s post for more.
The external change log exposes updates to OpenDJ in a well-defined way, great for your applications that need to be notified of changes. If you want to be able to test using the change log, you probably want to set it up with just one server rather than two or more. Have a look at Ludo’s post.