Weblogic Server Basic Components
WebLogic server is based on Java 2 Platform, Enterprise Edition (J2EE), the standard platform used to create Java-based multi-tier enterprise applications. WebLogic Server centralizes application services such as Web server functionality, business components, and access to backend enterprise systems. It uses technologies such as caching and connection pooling to improve resource use and application performance. WebLogic Server also provides enterprise-level security and powerful administration facilities.
A Weblogic server domain is an administrative grouping of servers and/or clusters. You configure, manage, monitor the domain from central location; this central location is the administration (admin) server.
Admin server is just a Weblogic Server instance which maintains a repository of configuration information for the domain. Admin server acts as a centralized application deployment server which provides browser based admin console for configure, manage and monitor all aspects of the domain.
A Managed server is a term for any other server in the domain other than the admin server. Managed Servers host the components and associated resources that constitute your applications – for example, JSPs and EJBs. When a Managed Server starts up, it connects to the domain’s Administration Server to obtain configuration and deployment settings.
Two or more Managed Servers can be configured as a WebLogic Server cluster to increase application scalability and availability.
Node Manager is a Java utility that runs as separate process from WebLogic Server and allows you to perform common operations tasks for a Managed Server, regardless of its location with respect to its Administration Server. If you run Node Manager on a machine that hosts Managed Servers, you can start and stop the Managed Servers remotely using the Administration Console or from the command line. Node Manager can also automatically restart a Managed Server after an unexpected failure.
WebLogic Server Cluster:
A WebLogic Server cluster consists of multiple WebLogic Server server instances running simultaneously and working together to provide increased scalability and reliability. A cluster is part of a particular WebLogic Server domain that appears to clients to be a single WebLogic Server instance. The server instances that constitute a cluster can run on the same machine, or be located on different machines. You can increase a cluster’s capacity by adding additional server instances to the cluster on an existing machine, or you can add machines to the cluster to host the incremental server instances. Each server instance in a cluster must run the same version of WebLogic Server.