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In a number of live presentations on the NCA concept, Larry Ellison, the founder and CEO of the Oracle Corporation, has frequently mused at what life would be like if common household appliances had the same complexity of maintenance as a PC. For example, you never hear someone say something like “Sorry, I can’t go out tonight, I’m staying home so I can upgrade my TV to version 7.0.” Nobody has to go to training class to learn how to use their washing machine. Nobody has to get a refrigerator adapter when they find out their latest leftovers aren’t compatible with their existing refrigerator. Yet computer users deal with these issues all the time. Software that runs on a Macintosh won’t run on a PC. Upgrading from one version of Windows to another is a significant effort. Ellison’s argument is that this is unacceptable, and, in order for computer technology to reach the masses, the PC must become as easy to use as any common household appliance.
In a recent presentation to a Japanese IT convention, Ellison was asked by a member of the audience if the network will be stable enough—won’t it crash from time to time? Isn’t it risky to place so much dependence on the network? Ellison’s response was to ask the audience member another question: what is the last thing that crashed on you: your telephone, or Windows 95? The audience roared with laughter, making the answer obvious. Yes, a network can experience problems once in a rare while, but when a network is maintained by a professional technical staff on a full-time basis, the burden of the rote, technical system maintenance is lifted off of the consumer, who can spend her time focusing on her actual work. We can just dial a phone number and start talking, not worrying about whether our phone has the same bit-switch error-checking parity as the phone of the person we’re calling.
The number of networks we already depend on is impressive: plumbing, electricity, highways, television, radio—all networks professionally run by others, that consumers use frequently, yet do not worry about personally maintaining, upgrading, or troubleshooting. Why should a computer user experience anything different?
Furthermore, in the NCA world, software is modularized so you only download those parts of the software that you need. If you just want to type a memo, no need to fire up the Granddaddy Power Word Processor 2200. You get the resources you need when you need them, regardless of their location on the network. The magic that makes this happen is the Oracle Web Application Server.
The Oracle WAS 3.0 is the Universal Application Server platform for the Network Computing Architecture model. It consists of one or more Web Listeners, Dispatchers, a Web Request Broker, and cartridges, or server-side applications.
The Web Listener, also known as the HTTP Daemon, or HTTP server, listens for requests from clients. When a client sends a request to the WAS across a network, using HTTP, the Listener receives it and determines what sort of request the client is making. If the request is for a static file or CGI script, it handles the request directly: it finds the appropriate static file, or executes the requested CGI script, and sends back the file or script output to the client. If the request is for an application, however, it forwards the request to the Dispatcher component.
The Listener can accept incoming requests from multiple IP address/port combinations.
Oracle’s WAS comes bundled with the Spyglass Web Listener, an independent product that is used as a Web server on its own. The bundled version is configured for use with the Oracle WAS. Other popular Web servers can be used instead, such as Netscape, Apache and Microsoft’s Webserver software, so if you’re already using one of those Webservers, you don’t have to change to integrate the WAS. The Installation Guide that comes with WAS contains instructions on how to configure those Web servers to work with WAS. Oracle has plans to integrate with other Web server software in the future.
The Dispatcher tracks server-side applications, and sends incoming requests to them, as they are received from the Web Listener.
The Listener and Dispatcher run together as one process, yet are distinct components. Multiple Listener/Dispatcher combinations can be run on the same machine or on different machines, allowing the WAS to handle multiple requests simultaneously, from different connections on different sets of ports. This can help to improve performance rather significantly, depending on your application performance requirements.
Even though they run as one process, the Dispatcher can work with any Listener, so if you choose not to use the bundled Spyglass listener, but instead configure a different Listener for use with the WAS, the Dispatcher will still function.
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