A high availability cluster includes two machines that are configured so that, if one machine (or application) is brought down, the second machine assumes the workload of both machines. Each of these machines is called one node of the high availability cluster. A high availability cluster is typically used in an environment that must always be available, for example, a banking system to which clients must connect continuously, 365 days a year.
Sybase’s Failover product enables Adaptive Server to work in a high availability cluster in an active-active configuration. That is, both the nodes in the cluster include Adaptive Servers managing independent workloads, and are capable of taking over each other’s workload in the event of a failure. The Adaptive Server that takes over the workload is called a secondary companion, and the Adaptive Server that fails is called the primary companion. Together they are companion servers. This movement from one node to another is called failover. After the primary companion is ready to resume its workload, it is moved back to its original node. This movement is called failback. Clients connected to the failed Adaptive Server automatically reestablish their network connections via the second machine.
You must tune your operating system to successfully manage both Adaptive Servers during failover. See your operating system documentation for information about re configuring your system for high availability.
An Adaptive Server configured for Failover can be shutdown
using the shutdown command only after you have
suspended it from companion configuration both at the server level
and at the platform level. See the configuration chapter of this
manual for your platform for more information
