Application layer
Quick answer
You scale by adding application-server instances, all connecting to the one database, with the message server balancing load across them.
Key takeaways
- The application layer consists of one or more application-server instances.
- The dispatcher distributes incoming requests to available dialog work processes and manages queues.
- Dialog: handle interactive user steps.
- Watch out: Misconfiguring work-process ratios, e.g. too few background processes.
What runs here
The application layer consists of one or more application-server instances. Each runs a set of work processes, controlled by a dispatcher, that execute the ABAP (and, where relevant, Java) code implementing SAP’s business logic. When a user acts, their request is handled here, and any data needed is fetched from the database layer.
Work-process types
- Dialog: handle interactive user steps.
- Background: run scheduled/batch jobs.
- Update: perform asynchronous database updates.
- Enqueue: manage locks to protect data consistency.
- Spool: handle printing and output.
The dispatcher and shared memory
The dispatcher distributes incoming requests to available dialog work processes and manages queues. Shared memory areas (buffers) cache frequently used data and programs so the system does not hit the database for everything, a major performance factor.
Scaling the application layer
You scale by adding application-server instances, all connecting to the one database, with the message server balancing load across them. This horizontal scaling is how SAP handles thousands of concurrent users.
Common pitfalls
- Misconfiguring work-process ratios, e.g. too few background processes.
- Ignoring buffering, poor buffering hammers the database.
- Assuming one instance in production sizing.
Want to learn this properly?
Our live, instructor-led SAP Training covers this hands-on, with real projects and a certification path.
Check your understanding
Which statement is true of Application layer?
- A. HANA security protects the database and its data through users, roles, privileges, encryption and auditing.
- B. The application layer consists of one or more application-server instances.
- C. Pricing in MM determines the price and conditions on purchasing documents, the net price, discounts…
Show answer
B. The application layer consists of one or more application-server instances.
Covered in the “What runs here” section of this lesson.
Which of these also applies to Application layer?
- A. Learning transactions in isolation, do the full flow.
- B. Each runs a set of work processes, controlled by a dispatcher, that execute the ABAP (and, where relevant…
- C. Guessing instead of using the reference tools.
Show answer
B. Each runs a set of work processes, controlled by a dispatcher, that execute the ABAP (and, where relevant…
Covered in the “What runs here” section of this lesson.
Which part of the Learn SAP curriculum covers Application layer?
- A. SAP interview questions
- B. SAP certification
- C. SAP architecture
Show answer
C. SAP architecture
This lesson sits in the SAP architecture section of the Learn SAP course.