An application server is a piece of software that sits at the centre of a multi-tiered networked computing environment, receiving requests from users, invoking applications and passing the results back.
It does this regardless of the operating system (OS) on which it is running. With more applications being written to run with an application server, programmers no longer have to address the OS.
This allows them to focus on the business requirements of their application. This might make life simpler for the developer, but what about end-users and VARs when it comes to buying these products?
To start with, there are two camps: Microsoft .Net and the open Java 2 Enterprise Edition (J2EE).
A survey of European system integrators by analyst Quocirca shows that, while in the past J2EE has been the preferred platform, .Net is becoming accepted. How do you choose? The main considerations are compatibility, maintenance and price.
Most J2EE application servers run on Unix, Linux, Windows and other OSs, while .Net runs on Windows servers only.
In a heterogeneous computing environment J2EE may be a requirement rather than a choice. But choosing a J2EE application server is not straightforward, because different suppliers extend their products beyond the J2EE standard to be competitive.
ISVs often make use of these extensions, which means they need multiple versions of their product, and not all ISVs support all application servers.
To further complicate things, some ISVs ship their products with an application server embedded. All of this means that the maintenance overhead of managing multiple servers is hard to avoid.
Can costs be contained? Prices are coming down. War has broken out in the J2EE world, where two products dominate: IBM WebSphere and BEA WebLogic.
There are other players - Oracle is aggressively targeting the market with Oracle 9i/AS and Sun has its own product, SunOne - but they are hedging their bets and backing WebLogic as well. Borland and Sybase also have products.
J2EE application servers are usually licensed per CPU. Prices vary according to vendor, but expect to pay about £7,000 per CPU for the full, unlimited product.
These prices can be prohibitive for smaller business and ISVs. Are there any less costly options out there?
This takes us back to Microsoft. Windows 2003 Server is available through Microsoft's normal channels; there is no additional charge for .Net, and Quocirca research shows that many systems integrators are now comfortable with deploying custom applications on .Net.
Entry-level pricing for a five-user system is about £700. Most J2EE vendors have cheaper offerings. IBM WebSphere Express, BEA WebLogic Express, Oracle 9i/AS Java Edition and Borland Enterprise Server Web Edition are cut-down versions of these products aimed at SMEs.
You can even get an application server for free. Novell has announced that NetWare 6.5 will include the Novell exteNd Application Server, allowing customers to run J2EE applications on NetWare.
The open source application servers JBOS and Tomcat are available for free. Oracle will provide Oracle 9i/AS free to ISVs, but its use would be limited to the ISV's application.
These cheaper options have a drawback: they are limited by either functionality or the environment in which they can be deployed.
It is applications themselves that add visible value to a business and you need to check that the limited application server can really support it. And remember, the ISVs will not have certified their applications against all of these products, especially the less popular ones.
Life might have got simpler for the programmer, but not for resellers and their customers. If you were starting from scratch you could standardise on a certain platform, although this might limit your choice of applications in the future.
If you are working with a systems integrator to build custom applications, they will advise on platforms, but Quocirca research shows that they cannot always make the decision for you.
In reality, most organisations do not have that simple choice. They carry baggage from the past that has to be integrated with the present and future.
Application servers do make the process of deploying applications in multi-tiered networked environments easier, but purchasing decisions and maintenance are as complicated as ever.
Bob Tarzey is service director at Quocirca.
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