What is and what do a WebLogic Server domain?

Question

I am a Java developer and I am pretty new in web application development using Java and I have the following doubts.

We are developing web app deployed on Oracle WebLogic Server.

What exactly is the weblogic domains? From what I understand each application use a definied domain. But what it exactly does?

Answer 1

From Oracle documentation:

A domain is the basic administrative unit of WebLogic Server. It consists of one or more WebLogic Server instances, and logically related resources and services that are managed, collectively, as one unit.

So it's an administrative container, you should think of the following: 1 domain equals 1 Administration Server.

The Administration Server:

A domain includes one WebLogic Server instance that is configured as an administration server. All changes to configuration and deployment of applications are done through the administration server.

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

• WebLogic Server Administration Console: Graphical user interface to the administration server.

• WebLogic Server Node Manager: A Java program that enables you to start and stop server instances—both administration servers and managed servers—remotely, and to monitor and automatically restart them after an unexpected failure.

• Note that the node manager is installed on all the machines that host any server instance – both administration server and managed servers.

Answer 2

This link from oracle docs has precisely defined weblogic domain.It has detailed the various ways of dividing your application may be logically,physically or based on size.Specifically below sections from the link might answer your question

What Is a Domain?

Organizing Domains

https://docs.oracle.com/cd/E13222_01/wls/docs103/domain_config/understand_domains.html

I found the below link useful as well:

http://middlewaremagic.com/weblogic/?p=1914

Answer 3

A WebLogic Domain is a concept that represents an environment.

• A Domain includes an Administration Server, and 1 or more Managed Servers
• Managed Servers are basically Java servers running on the physical machine or VM, which can each contain 1 or more Managed Servers.
• Managed Servers can be organized into Clusters
• A Domain also contains Resources, such as database connections pools, which can be used by Applications.

• Applications and Resources are deployed on to specific Managed Servers or Cluster(s) (a Resource should be deployed on the same Managed Server or Cluster as the Application that needs it)

• A Domain usually contains multiple applications.

• Clusters abstract the Managed Servers as a group, so it's easy to scale an Application deployment by adding Managed Servers to a Cluster.

• Multiple Clusters in the same Domain can help segregate Applications and Resources according to their usage requirements.

• Dynamic Clusters include rules for scaling the number of Managed Servers in and out according to specific metrics.

Furthermore:

• There is 1 Admin Server per Domain. Usually there is 1 Domain per group of machines running Managed Servers in the Domain.
• While the Admin Server manages what is deployed where, another service, the Node Manager, runs on each physical machine or VM to manage the life-cycle of the Managed Server (start, stop, health check) and reports to the Admin Server.