Defining an R/3 System and Instance

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Defining an R/3 System

The simplest definition of an R/3 system is "one database." In one R/3 system, there is only one database. To expand the definition, R/3 is considered to be all of the components attached to that one database. One R/3 system is composed of one database server accessing a single database, one or more application servers, and one or more presentation servers.

By definition, it is all of the components attached to one database. If you have one database, you have one system. If you have one system, you have one database. During an implementation, there is usually one system (or one database) assigned to development, one or more systems designated for testing, and one assigned to production.

The term R/3 system landscape denotes a description of the number of systems within an SAP installation and how they are designated, such as development, test, or production.

Defining an R/3 Instance
When you hear someone say the word instance, most of the time, that person will be referring to an application server. The term instance is synonymous with application server.

The term central instance refers to the database server. If an application server and database server both reside on the same machine, the term central instance refers to the computer on which both reside.

In the most general terms, an instance is a server. It is a set of R/3 processes providing services to the R/3 system.