Client / Server Architecture in R/3

The three-tire client /server architecture consist of a presentation layer, an application layer, and a database layer

Hardware Point: these three layer can run separately on different computers or all together on the same computer.

Presentation Layer
The presentation layer in R/3 is consist of the SAP Graphical User Interface (SAPGUI)
The SAPGUI (SAP Graphical User Interface) accepts the user input and passes it ot the next layer the application layer for the further processing the SAPGUI accept the data from the application layer and presents the data to the user. Each R/3 session is performed thorough a SAPGUI.

The Application layer
User requests are passed from the presentation layer to the R/3 application layer. This is where the actual calculations and evaluation are preformed. Data that is needed to perform these calculations and evolutions is requires from the database layer. The incoming data is processed by the application layer and passed to the database.

The Database Layer
The database layer consists of a relational Database Management System (RDBMS). Data is exchanged between the application processes and the RDBMS through the SQL interface. The data is an R/3 System is stored in one database on one computer. The name of the database determines the name of the R/3 System this name is consist of three characters either uppercase letters and or numbers bases ex D10, K11 (the first character must be an uppercase letter) The abbreviation SID (short System Identifier)

The database administrator task
1. Database backup and data restorations if error occur
2. Configuration
3. Flow control and optimization
4. Memory management
5. Data reorganization
6. Software maintenance and installation

Internet Transaction Server
The R/3 System is connected to the internet through the Internet Transition Server. The ITS consists of two software components the A-gate process(Application Fate) and the W-gate process(web Gate)

A-gate process establishes the connection to the R/3 application server

W-gate process establishes the connection to the web server. Both components communicate with each other using the TCP/IP protocol.
(Dynamic Information and Action Gateway protocol)
ISAPI (Microsoft Information server API)
Internet Application Components (IACs)

Client
From a commercial law, organizational and technical viewpoint, a closed unit within an R/3 System with separate master records within a table.

A Client is an independent business unit within the R/3 System

Default Clients
The R/3 System contains the default clients. 000, 001, and 066. You should not make any changes to these clients. 000 is used specifically for R/3 release upgrades and to import certain R/3 configuration settings. Settings made in these client are usually valid throughout the whole R/3 System.