If the primary cluster fails, the application must be switched over to the secondary cluster as soon as possible. To enable the secondary cluster to take over, the DNS must be updated. In addition, the secondary volume must be mounted on the mount point directory for the application file system.
The DNS associates a client with the logical hostname of an application. After a failover or switchover, the DNS mapping to the primary cluster must be removed, and a DNS mapping to the secondary cluster must be created. The following figure shows how the DNS maps a client to a cluster.
To update the DNS, use the nsupdate command. For information, see the nsupdate(1M) man page. For an example of how to cope with a failover or switchover, see Example of How to Cope With a Failover or Switchover.
Synchronize the primary cluster with the secondary cluster to ensure that the primary volume is up-to-date.
Update the DNS so that clients can access the application on the primary cluster.
Mount the primary volume on to the mount point directory for the application file system.