Administration server

A domain includes one Oracle WebLogic Server instance that is configured as an administration server. You make all changes to the configuration and deployment of applications in the administration server.

The administration server provides a central point for managing the domain and providing access to the Oracle WebLogic Server administration tools. These tools include the following:

• Administration Console. A graphical user interface (GUI) to the administration server. For more information about the Administration Console, see Oracle WebLogic Server Administration Console.
• Node Manager. A Java program that enables you to start and stop server instances remotely and to monitor and automatically restart them after an unexpected failure. For more information about Node Manager, see Oracle WebLogic Server Node Manager.

Managed servers

All Oracle WebLogic Server instances other than the administration server in a domain are called managed servers. Managed servers host application components and resources, which are also deployed and managed as part of the domain. In a domain with only a single Oracle WebLogic Server instance, that single server works as both the administration server and the managed server.

NOTE:  All managed servers in a domain must run the same version of Oracle WebLogic Server. The administration server can run either the same version as the managed servers in the domain or a later service pack.

Clusters

A domain might also include Oracle WebLogic Server clusters, which are groups of managed server instances that work together to provide scalability and high availability for applications. Clusters can improve performance and provide failover when a server instance becomes unavailable. In a clustered environment, failover is when one node fails but transactions continue to process on other nodes with no interruption of the end-user experience. The servers within a cluster can either run on the same computer or reside on different computers. For more information about clusters, see About Oracle WebLogic Server Clusters. For more information about failover, see Siebel Self-Service Application Developer's Guide on Siebel Bookshelf.

NOTE:  The Siebel Bookshelf is available on Oracle Technology Network (http://www.oracle.com/technetwork/indexes/documentation/index.html) and Oracle Software Delivery Cloud. It might also be installed locally on your intranet or on a network location.