R/3 system is based on Client/Server architecture
that is comprised of three tiers:
server: Your local PC that has SAPGUI.
server: The application server is used to run the business
application programs in the R/3 client/server concept. The
application modules are loaded from the data base server
to the application server as required. Thus the application
server requires only storage capacity to accommodate UNIX,
Swapping and the SAP runtime environment.
server: The data base server stores the SAP application
programs and data in the R/3 client/server concept. It also
handles the SAP update program and batch jobs.