Sybase Failover allows you to configure two version 12.0 and later Adaptive Servers as companions. If the primary companion Adaptive Server fails, that server’s devices, databases, and connections can be taken over by the companion Adaptive Server.
You can configure a high availability system either asymmetrically or symmetrically.
An asymmetric configuration includes two Adaptive Servers that are physically located on different machines, but share the same system devices, system/master databases, user databases, and user logins. These two servers are connected so that if one of the servers is brought down, the other assumes its workload. The companion Adaptive Server acts as a “hot standby” and does not perform any work until failover occurs.
A symmetric configuration also includes two Adaptive Servers running on separate machines, but each Adaptive Server is fully functional with its own system devices, system/master databases, user databases, and user logins. If failover occurs, either Adaptive Server can act as a companion for the other Adaptive Server.
In either setup, the two machines are configured for dual access, which makes the disks visible and accessible to both servers.
In a replication system, where Replication Server makes many connections to Adaptive Servers, you can enable or disable Failover support of the database connections initiated by a Replication Server to Adaptive Servers. When you enable Failover support, Replication Servers connected to an Adaptive Server that fails are automatically switched to the companion machine, reestablishing network connections.
See the Adaptive Server Enterprise documentation for more detailed information about how Sybase Failover works in Adaptive Server. See Appendix B, “High Availability on Sun Cluster 2.2” for information about Failover support for Replication Server.
