Components of a domain

Following are the basic Components of a domain

              Admin Server

              Managed Server

              Cluster

              Machine

              Node Manager

Admin Server:

• One of the weblogic server instances is Admin server which runs using JVM (Java Virtual Machine).
• Central configuration controller for the entire domain
• Hosts the Administration console.
• Enables you to start and stop servers from a central location.
• Enables you to migrate servers and services within domain
• Enables you to deploy applications within the domain

Guidelines:

• There must be exactly one Administration server in domain
• An Administration server controls only one domain.
• For production use, we recommend not to hosting application logic or resources on the Administration server.

Managed Server:

• A running instance that hosts applications and resources needed by those applications- The real work horses in a weblogic domain
• Each Managed server is independent of all other managed servers in the domain (unless they are in cluster)
• You can have as many Managed Servers in a domain as you need.
• Individually Managed Servers are typically added for capacity and application isolation.

Admin server to managed server Interaction:

• The Administration server stores the master copy of the domain configuration, including the configuration for all managed servers in the domain
• Each manages server stores a local copy of its configuration.
• When managed server starts, it connects to the Administration server to synchronize the configuration
• When configuration is changed, the Administration server sends changed configuration to managed server

Cluster

• Group of managed servers.
• Same version managed servers can be clustered but not of different versions.
• Any number of clusters can be created.

Machine

• A machine definition is used to associate a computer with the managed server it hosts.
• Used by Node Manager in restarting a failed Managed server
• Used by a clustered Managed Server in selecting the best location for storing replicated session data

Node Manager

          Responsible for starting and stopping the managed servers.