Presentation, Application ,Database Servers In SAP R/3

Application Server-: 

The application layer of an R/3 System is made up of the 

Application servers and the message server. Application 

Server is placed between the presentation server and database server. 

Application programs in an R/3 System are run on application servers. 

The application servers communicate with the presentation Components, 

the database using the message server. All the data are stored in a 

Centralized server. This server is called database server. The message 

server is used to communicate between different servers.

Presentation server in sap-:

Presentation server is system with GUI means all the output you can seen 

their and all the input is inserted by the presentation server. it collect 

the requirements from end users and dispatcher dispatch it to the data base 

layer for the response of that, where data base server is the main server 

which consist all the data information and tables, application server  placed 

between both, presentation and Database server and it provides interfacing 

between the database & presentation server. But now a new concept is introduced 

that is netweaver concept, in which a new layer is introduced that is internet 

layer. it consist every server different so it is called R/3 system earlier single

 System consist all the servers that is called R/1.