HP Serviceguard Toolkits for Database Replication Solutions User Guide (August 2011)

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 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.
16 Serviceguard toolkit for Oracle Data Guard