Oracle WebLogic Server 

•The Number #1 Java EE application server, designed for the most Mission-Critical of applications
•Developer-friendly – productive, standards-based development
•Focus on quality of service – performance, scalability, reliability, availability
•Built-in manageability – configuration, monitoring , diagnostics, maintenance

Domain•a logically related group of WebLogic Server instances that you manage from a single set of configuration artifacts.
•What’s in a domain?
•Servers
•Clusters of servers
•Rules:
•All WebLogic Server instances within the same domain must be at the same major and minor version.
•Servers within a domain can be at different Maintenance Pack levels as long as the Administration Server is at the same Maintenance Pack Level or higher than its Managed Servers.

Server
•A configured instance to host applications and resources
•WebApps, Enterprise Apps, Web Services, …
•JMS, JDBC, Diagnostics, …
•
•What types of servers are there?
•Administration Server
•Managed Server

Administration Server
•Central configuration controller for the entire domain
•What else does it do?
•Hosts the Administration Console
•Enables you to start and stop servers from a central location
•Enables you to migrate servers and services within the 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 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 a cluster, defined later)
•You can have as many Managed Servers in a domain as you need
•Individual Managed Servers are typically added for capacity and application isolation

Administration 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 Managed Server stores a local copy of its configuration.
•When a 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 Servers

Cluster
•A cluster is a group of Managed Servers running simultaneously and working together to provide increased scalability and reliability
•Scalability: through parallelism
•Reliability/Availability: through replication and redundancy
•A cluster appears as a single instance to most clients.
•Clusters enable some advanced features, such as Whole Server Migration, Service Migration, and clustered JMS destinations.

Node Manager
•Utility/process running on a physical server that enables you to start, stop, suspend, and restart WebLogic Server instances remotely
•Must run on each physical server that hosts WebLogic Server instances that you want to control with Node Manager
•Not associated with a domain. Can start any server instance that resides on the same physical server.
•Optional, but required to start/stop servers using the Administration Console
•Required for Whole Server Migration and for some configurations of Automatic Service Migration

Machine
•A definition that identifies a particular, physical piece of hardware.
•A machine definition is used to associate a computer with the Managed Servers 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

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