An application server is a Java Virtual Machine (JVM) that runs user applications. The application server collaborates with the web server to return a dynamic, customized response to a client request. The client request can consist of servlets, JavaServer Pages (JSP) files, and enterprise beans, and their supporting classes.
For example, a user at a web browser visits a company website:
When you install the product, a default application server, named server1, is automatically created. You can use the administrative console to manage this server.
You can use the administrative console or command-line tools to create additional application servers that can either be separately configured processes or nearly identical clones. You must either use command-line tools to manage these additional servers, set up an administrative console for each server, or configure an administrative agent to provide a single interface to all of your servers, including the original base server. An administrative agent makes it easier to more fully administer these unfederated application servers.
You can improve system performance if you configure some of your application servers, such that each of their components are dynamically started as they are needed, instead of letting all of these components automatically start when the server starts. Selecting this option can improve server startup time, and reduce the memory footprint. Starting components as they are needed is most effective if all of the applications that are deployed on the application server are of the same type. For example, using this option works better if all of your applications are web applications that use servlets, and JavaServer Pages (JSP). This option works less effectively if your applications use servlets, JSPs and Enterprise JavaBeans (EJB).
You can also perform the following tasks to enhance the operation of an application server:
The product supports asynchronous messaging based on the Java Message Service (JMS) of a JMS provider that conforms to the JMS specification Version 1.1.
The JMS functions of the default message service that is provided with the product are served by one or more messaging engines (in a service integration bus) that runs within application servers.
A generic server is a server that is managed in the WebSphere administrative domain, although it is not a server that is supplied by the product. The generic server can be any server or process that is necessary to support the product environment.