Domain, Admin Server, Node Manager, Managed Servers

 Domain

A Domain is a logic group of WebLogic Server resources that you mange as a unit. A domain provides single point of administration for all WebLogic Server resources.

A WebLogic domain can logically separate: Development, Test, Staging and Production Applications.

 

A server is an instance of WebLogic Server executing in a JVM. A Server runs on a designated WebLogic machine. It has a dedicated amount of RAM and it is multi-threaded.

Admin Server

Admin Server is an instance of  WebLogic Server. It maintains the configuration information for the domain. It runs the WebLogic Administration Console. WebLogic Domain contains only one Admin Server. The failure of an Administration Server does not affect the operation of Managed Servers in the domain but it does prevent you from changing the domain's configuration.

Managed Server

Apart from Admin Server any other instance of WebLogic Server is called Managed Server. A managed Server contacts admin server for configuration information. Managed Server runs the business applications in a production environment. Managed Servers can run independently even when the admin Server is down. 

To optimize performance, Managed Servers maintain a read-only copy of the domain's configuration document. When a Managed Server starts up, it connects to the domain's Administration Server to synchronize its configuration document with the document that the Administration Server maintains

Machine

A machine is a computer that hosts WebLogic Servers. A machine Runs a supported operating system platform. A machine can host multiple WebLogic Server Instances.

Cluster

A Cluster is a logical group of WebLogic Servers. WebLogic Cluster provides Failover, High Availability  and Load balancing. Admin Server is not part of Cluster. Only Managed Server Instances can be part of Cluster. 

Node Manager

Node Manager is a WebLogic utility used to start, stop and restart WebLogic Server Instances. We can start Admin and Managed Servers with or with out node manager but when you want to start or stop the Admin and Managed Server instances from remote location like a web browser or from other remote machine then node manager configuration is necessary. 

Proxy Server

A proxy server forwards requests to the other machines. It can be used as a level of indirection and security. It can be used to load balance a system.

Firewall

Firewalls provide filtering, authorization and authentication services. Firewalls help keep out of hackers. Firewalls map port requests. They can act as proxy servers. It can decrease back end network activity.