WebSphere Application Server

WebSphere Application Server (informally nicknamed WAS), part of the Distributed Application & Web Servers subcategory of products, is the flagship product in WebSphere, one of the brands in the IBM Software Group. WAS is a J2EE application server.

There are several versions of WAS (the support lifecycle dates are current as of March 2007):

Version 6.1 – Java SE 5 and J2EE 1.4 (became available on 30-Jun-2006; still supported and marketed)
Version 6.0 – J2SE 1.4 and J2EE 1.4 (became available on 18-Feb-2005; still supported and marketed)
Version 5.1 – J2SE 1.4 and J2EE 1.3 (became available on 16-Jan-2004; no longer marketed, but still supported)
Version 5.0 – J2SE 1.3 and J2EE 1.3 (became available on 03-Jan-2003; support ended on 30-Sep-2006)

For each version, there are several editions of WAS (comparison):

WebSphere Application Server Community Edition (WAS CE) – An open-source version, lighter-weight edition of WAS based on Apache Geronimo
WebSphere Application Server - Express (WAS Express) – WAS Base with limited capacity plus rapid development tools (simplified Rational Web Developer for WebSphere); designed to be easier to install and use, but less flexible
WebSphere Application Server (WAS Base) – A single J2EE application server, but no clustering; supports AIX, HP Unix, Linux, Sun Unix, and Windows (including Linux on system z9/zSeries)
WebSphere Application Server Network Deployment (WAS ND) – Multiple J2EE application servers with clustering; each server is essentially WAS Base
WebSphere Application Server for i5/OS (WAS i5/OS) – WAS Express/Base/ND, but for System i running i5/OS
WebSphere Application Server for z/OS (WAS z/OS) – WAS ND, but for System z running z/OS

A related product is WebSphere Extended Deployment (WXD), which dynamically adjusts the number of servers running each application to maximize meeting SLAs based on application priority.

Details

I have a WAS thread on my blog.

A significant new feature added in WAS V6.0 is the Service Integration Bus.

Good to know:

Documentation is in the WAS library, including the WAS 6.1 InfoCenter.
You can get formal help by contacting IBM Software Support.
You can get help from your fellow developers on the developerWorks WebSphere Application Server forum.
The best IDE for developing J2EE apps for WAS is Rational Application Developer.
You can find a list of the best WAS articles at J2EE and WebSphere Application Server Recommended reading list.
You can download a trial install of WAS V6.1.
WebSphere Application Server System requirements lists what software and hardware is required and supported to run WAS
WebSphere Application Server Support Lifecycle and IBM Software Support Lifecycle list when products become available and when support ends. The IBM Software Support Lifecycle Policy explains the rules for how long support lasts.
Keep your installs up-to-date by following the guidance in:
Also see WebSphere Learning Resources.

Common issues: