Sun Java System Reference Configuration Series: Portal Service on Application Server Cluster

Service Availability

Service availability means that a service is available, even when a service provider fails. Service availability is generally achieved using multiple identically configured service instances (redundancy). Redundancy eliminates single points of failure (assuming that simultaneous failure of all instances is extremely unlikely). If one instance providing a service fails, another instance is available to take over. This mechanism is known as service failover.

Service failover is supported in the reference configuration through two mechanisms: