cluster with two nodes and a shared disk. The standby database instance is started on any one node in the third location, the database and the archived logs are located on the shared disk. If high availability is not needed for the standby database, the third location may not be configured in a Serviceguard cluster. In this situation, there will only be one server at the third location and the standby database instance must be brought up manually.
HP recommends that you do not configure the standby database in the same Metrocluster as the primary database. This occurs because a Metrocluster with two data centers, in which the primary database package is running on the first site, replicates (hardware replication from array to array) to the second site. If the standby database is configured on the second site of the Metrocluster it becomes redundant configuration.
If there is a disaster and Data Center 1 is down, the primary database instance is failed over to Data Center 2 and continues to function as a primary database. There will be no problems in starting the primary database at Data Center 2 using the replicated data from the shared disk. This is because Metrocluster has achieved data replication from Data Center 1 to 2. After the primary database instance comes up at Data Center 2, it continues to send the archived logs to the standby database located at the third location.
Also, a configuration in which another primary instance of Oracle is running at the second site, and replicates to a third location is possible.
Figure 9 Data Guard setup in an EDC environment
HP Serviceguard Extended Distance Cluster (EDC) is a special configuration of an HP Serviceguard cluster. It allows the cluster to span across two separate data centers for increased availability and protection against an outage that might affect one of the data centers. HP Serviceguard EDC provides automatic or manual failover capabilities for