HP Serviceguard Toolkits for Database Replication Solutions User Guide, March 2012

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 mission-critical data and applications in
data centers up to 100 kilometers apart. It protects geographically dispersed data centers from
unplanned downtime caused by system and application failures, operator errors, and local disasters.
In addition, it enhances data and application availability.
Figure 9 (page 16), shows a Data Guard setup in an EDC environment. All the four nodes are
present inside the same Serviceguard cluster. Primary database is configured at Site A and standby
database is configured at Site B. The primary package can failover in Site A but must not be
configured to failover to Site B. Similarly, standby database can failover inside Site B but must not
be configured to failover to Site A.
When Site A goes down, the role of standby on Site B must be manually changed to primary,
because role transitions are not supported in this configuration.
NOTE: This configuration is supported both in single-instance and RAC environments. For better
understanding, the packages in the Figure 9 (page 16) are shown for a single-instance database.
16 Serviceguard toolkit for Oracle Data Guard