The HADB software is supplied with the Application Server standalone distribution of Sun Java System Application Server. For information about available distributions of Sun Java System Application Server, see Distribution Types and Their Components in Sun Java System Application Server 9.1 Installation Guide. HADB features are available only in the enterprise profile. For information about profiles, see Usage Profiles in Sun Java System Application Server 9.1 Administration Guide.
If you have two active HADB nodes, you can configure two spare nodes (on separate machines), that can take over in case of failure. This is a cleaner method because backup and restore of HADB may result in stale sessions being restored.
For information on creating a database with spare nodes, see Creating a Database. For information on adding spare nodes to a database, see Adding Nodes. If recovery and self-repair fail, then the spare node takes over automatically.