application server question?

Question

Can somebody explain what application server is? I am trying to understand SAP. In their 3 tier layout, you have the server, the application server and then the client computer. My question is why can't you just use a client computer with the application and use it to talk to the database residing within the server. What's the point of having the client server talk to the application server who then talks to the server?

Is it because these client computers are relatively "crappy" and they only possess enough power to display the GUI? IE a cash register at Target.

Thanks

great, thanks for the clarification...Yahoo requires 4 hours before I can assign points?...

As far as the Oracle vs SAP debate.....Oracle is a middleware provider and more/less open source? Like they provide the database technology and then their middleware is based on a template so its easily accessible to the database?

Whereas SAP goes all the way by providing the server, and the applications via modules which are customizeable...

If you have any links that explains these in plain terms it would be great. Thanks!

Answer 1

The application servers is just a way to optimize the connection bewteen the client and the server(s). You can of course imagine a 2 tier layout but the communication is less efficient.

Check the SAP help portal and the SAP SDN for more information.
Getting Started with SAP NetWeaver Application Server

One goal of the SAP NetWeaver Application Server (SAP NetWeaver AS) is to provide a way to develop Java applications that can easily reach back into the world of ABAP code. Another, perhaps more important goal, is to provide the premier interactive development environment for the J2EE platform. The following features serve one or both purposes:

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SAP NetWeaver Developer Studio
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J2EE 1.3 Support
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ABAP Engine
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Web Dynpro
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Open SQL
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Java Dictionary
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Java Development Infrastructure

SAP NetWeaver Developer Studio

SAP NetWeaver Developer Studio is an Eclipse-based interactive development environment that is created to increase developer productivity in SAP NetWeaver AS. The environment is enhanced with plug-ins that perform specific functions for developers to bring together all of the different elements of SAP NetWeaver AS in a unified manner.

J2EE 1.3 Support

SAP NetWeaver AS 6.40, which is in general release since January 2004, provides full support for the J2EE 1.3 platform. This means that any J2EE-compliant development environment or technology can work with the SAP engine.

ABAP Engine

The ABAP Engine of the SAP NetWeaver AS allows you to develop and run ABAP-based applications within the server. It provides all services and features known from the long established ABAP development and runtime environment formerly known as Basis from SAP.


Web Dynpro

Web Dynpro is SAP's development environment for creating professional User Interfaces for business applications which includes sophisticated runtime services. Its model-driven approach minimizes manual coding and uses visual tools to design and reuse UI components. Web Dynpro is based on a powerful and flexible Model-View-Controller architecture which ensures a clear separation of User Interfaces and backend services. Developers have full control of the generated code at all levels of the development process.

OpenSQL

OpenSQL is an abstraction of the database that allows for more platform independence than JDBC. Building on the ABAP version of OpenSQL, the Java implementation allows a direct relational interface or an object-based interface to be used to access data with very little work on the part of the developer.

Java Dictionary

Java Dictionary is the incarnation of the ABAP Data Dictionary in the world of J2EE. SAP decided to implement this concept in SAP Web AS to provide a central location for defining data types used by Web Dynpro and OpenSQL.

Java Development Infrastructure

The Java Development Infrastructure overcomes the limitations of file-based source code control systems by creating development components to which Java source code files are assigned. Using the design time repository and the component build service, SAP NetWeaver Developer Studio provides increased productivity by helping manage dependencies and avoiding complete recompilations when only a small change was made.


http://help.sap.com/saphelp_nw2004s/helpdata/en/6a/69f45201356248830f1e70fdd7178e/frameset.htm

Answer 2

You've more or less hit the nail on the head. "Application Servers" become a buzzword whenever Business starts looking at thin clients (stripped computers) as a way to cut costs. The idea is fairly simple: The app server houses the application (which is convenient from several perspectives, including software licensces) and provides the bulk of the computing power & storage required to run the application. It also serves as a middle tier for the database, with the client computer simply displaying the GUI and communicating changes in state to the app server.

You absolutely can use a client computer with a copy of the application and have it configured to use a centralized database, this is just a different design strategy, with it's own pros and cons.