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A server cluster is a group of two or more servers that are configured so that if one server fails, another server can take over application processing. The servers in a cluster are called nodes. Typically, these servers store data on a common disk or disk array.
When a clustered Siebel Server fails, all the applications and services on the server stop. Application users must reconnect and log in to the server that takes over. For example, if the Siebel Server that failed was hosting Siebel Communications Server, the communications toolbar is disabled, and users must reconnect and log in to the new server.
Cluster vendors can validate their third-party server cluster products to provide server clustering for deployments of Siebel Business Applications. For validation assistance, contact your Oracle sales representative for Oracle Advanced Customer Services to request assistance from Oracle's Application Expert Services. For recommendations and help on the use of cluster products with Siebel Business Applications, customers should contact the cluster vendor of their choice.
An active-passive server cluster contains a minimum of two servers. One server actively runs applications and services. The other is idle. If the active server fails, its workload is switched to the idle server, which then takes over application processing.
Because the standby server is idle, active-passive server clusters require additional hardware without providing additional active capacity. The benefit of active-passive clusters is that, after a failover, the same level of hardware resources is available for each application, thereby eliminating any performance impact on users. This benefit is particularly important for performance-critical areas such as the database. The most common use of active-passive clusters is for database servers.
An active-active server cluster contains a minimum of two servers. Both actively run applications and services. Each may host different applications or may host instances of the same application. If one server fails, its processing load is transferred to the other.
Some Siebel Server components, such as Siebel Connection Broker (SCBroker), Siebel Gateway Name Server, Synchronization Manager (Siebel Remote), and Siebel Handheld synchronization listen on a configurable static port. When these components run in an active-active cluster, you must plan your port usage so there is no port conflict after failover.
For example, an active-active server cluster contains two platforms, each running a Siebel Server. If one platform fails, the other will host two Siebel Servers. Siebel Servers include several services, such as Siebel Connection Broker, that use a dedicated port. If this port number was the same on both platforms, there will be a port conflict after failover.
Active-active clusters use all the server platforms continuously. Consequently, they take better advantage of computing resources than active-passive clusters. When doing capacity planning, make sure that clustered servers have sufficient capacity to handle a failover. Because failovers are usually infrequent and normally last only a short time, some performance degradation is often acceptable.
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