The entire Websphere configuration is saved and persisted within XML files. These XML configuration files are arranged in a cascading hierarchy of directories which reflects the internal structure of the application server so, for example, the WAS top element, the Cell, reflects in the cell.xml file, which provides configuration data for the Cell. On the other hand, the server.xml file provides configuration for a server component.
Although you will rarely need to modify manually the XML configuration files, by looking at their structure you to understand which are the key components of the WAS infrastructure. The first recipe of this chapter covers these details. In the next recipes we will learn how to get started with the core Management tool which is the Web based Admin console.
Websphere core components
WAS is structured internally in a set of different components which allow a flexible definition of your configuration. The component that has the widest scope is the Cell.
A Cell is a grouping of nodes into a single administrative domain. A Cell contains a Deployment Manager and one or moreNodes.
In WebSphere terms, this means that if you group several Servers within a Cell, then you can use one admin console to administer them.
The Deployment Manager is a service that manages all Nodes in the cell.
The Deployment Manager is responsible for managing the installation and maintenance of Applications, Connection Pools and other resources related to a JEE environment. It is also responsible for centralizing user repositories for application and also for WebSphere authentication and authorization. You can manage all these resources from the Websphere Admin Console.
The Node is another virtual unit that is built of a Node Agent and one or more Server instances.
The Node Agent is a service that is used to communicate with the Deployment Manager.
The Node Agent is responsible for spawning and killing server processes and as well for configuration synchronization between the Deployment Manager and the Servers.
The last piece of the WAS configuration is the Server.
Servers are regular Java process responsible for serving JEE requests. The server name corresponds to the actual name of the application server JVM’s.
And to finish, Clusters are also virtual units that groups Servers so that resources added to the Cluster are propagated to every Server that makes up the cluster. The following picture depicts the Websphere core components giving an overview of the concepts exposed so far: