⟩ Please explain what is an application, presentation and database servers in SAP R/3?
The application layer of a R/3 system is made up of the application server and the message server. Application programs in an R/3 system run on application servers. Using the message server, the application servers communicate with presentation components, the database and also with each other. All the data are stored in a centralized server, which is known as a database server.