Cluster managers and high availability disaster recovery (HADR)

Set up an HADR pair where the primary and standby databases are serviced by the same cluster manager

This configuration is best suited to environments where the primary and standby databases are located at the same site and where the fastest possible failover is required. These environments would benefit from using HADR to maintain DBMS availability, rather using crash recovery or another recovery method.

You can use the cluster manager to quickly detect a problem and to initiate a takeover operation. Because HADR requires separate storage for the DBMS, the cluster manager should be configured with separate volume control. This configuration prevents the cluster manager from waiting for failover to occur on the volume before using the DBMS on the standby system. You can use the automatic client reroute feature to redirect client applications to the new primary database.

Set up an HADR pair where the primary and standby databases are not serviced by the same cluster manager

This configuration is best suited to environments where the primary and standby databases are located at different sites and where high availability is required for disaster recovery in the event of a complete site failure. There are several ways you can implement this configuration. When an HADR primary or standby database is part of a cluster, there are two possible failover scenarios.

• If a partial site failure occurs and a node to which the DBMS can fail over remains available, you can choose to perform a cluster failover. In this case, the IP address and volume failover is performed using the cluster manager; HADR is not affected.

• If a complete site failure occurs where the primary database is located, you can use HADR to maintain DBMS availability by initiating a takeover operation. If a complete site failure occurs where the standby database is located, you can repair the site or move the standby database to another site.