SAP architecture
SAP’s classic architecture is a three-tier client-server model, presentation, application and database, introduced with R/3 and still the mental model for how SAP systems are structured. Grasping it makes installation, performance and troubleshooting far clearer.
Around the core sit the gateway (for RFC/external communication), and mechanisms like RFC, BAPI, IDoc and ALE that let SAP talk to other SAP and non-SAP systems, the subject of the architecture and integration modules.
- On the application layer, user requests are handled by work processes of different types (dialog, background, update, enqueue…
- An SAP system is made of instances, each a set of work processes and memory on a server.
- Presentation layer: what the user sees, SAP GUI or, increasingly, the Fiori web UX in a browser.
- Watch out: Confusing the tiers, presentation is not where business logic runs.
The three tiers
- Presentation layer: what the user sees, SAP GUI or, increasingly, the Fiori web UX in a browser.
- Application layer: one or more application servers running the ABAP (and, in S/4HANA, some Java/BTP) work processes that execute business logic.
- Database layer: the single database holding all data, HANA for S/4HANA, or traditional databases for older systems.
Work processes and the dispatcher
On the application layer, user requests are handled by work processes of different types (dialog, background, update, enqueue, spool) coordinated by a dispatcher. This division is why SAP can serve interactive users and heavy batch jobs on the same system without one starving the other.
Instances and scaling
An SAP system is made of instances, each a set of work processes and memory on a server. You scale by adding application-server instances behind message-server-based load balancing, all sharing one database. This is horizontal scaling of the application tier, much like other enterprise systems.
Integration components
Around the core sit the gateway (for RFC/external communication), and mechanisms like RFC, BAPI, IDoc and ALE that let SAP talk to other SAP and non-SAP systems, the subject of the architecture and integration modules.
Common pitfalls
- Confusing the tiers, presentation is not where business logic runs.
- Ignoring work-process types, misconfigured ratios cause bottlenecks.
- Assuming one server, production systems are multi-instance.
Authoritative sources
- - SAP NetWeaver and system architecture docs