Defining the ABAP Platform Landscape

In this lesson, you will learn about the basic architecture of the ABAP Platform. You'll learn how SAP defines a "system" and what system components make up the application layer.

In Unit 1, you learned that the ABAP Platform uses a three-tier client-server architecture to manage and execute business applications.

These tiers consist of the presentation layer, the application server layer, and the database layer. An individual SAP system is defined logically by this architecture.

The presentation layer is where the user interface is located, SAP GUI, the SAP Business Client, and/or SAP Fiori. It is where users interact with the application and input or retrieve data. The user interface runs on a supported PC, laptop, tablet, or mobile device.

The application layer is where the business logic and transaction processing of the application takes place. It handles requests from the presentation layer and communicates with the database layer to retrieve and store data. The application layer consists of one or more application servers or application instances.

The database layer is where the actual data is stored and managed. Each SAP system has its own separate database instance or tenant. In SAP S/4HANA, the database is SAP HANA.

Finally, each SAP system is identified by a unique System ID or SID. The SID must be defined using the following rules. The SID must possess the following properties:

• Unique, each SID must be unique
• Three characters long
• Alphanumeric
• Begin with a letter (upper case)
• No keywords allowed

Examples include: D01, QA7, PR1, DEV

In addition to these three layers, the ABAP Platform also includes various infrastructure components such as the ABAP runtime environment, development tools, and integration with other SAP modules and services. These components work together to provide a complete and robust platform for developing and running enterprise-grade applications within the SAP ecosystem. Let's explore the application layer further to learn about the architecture of an SAP application server.

An SAP application server, also known as an SAP instance, is a collection of resources and processing capabilities. An SAP instance is an administrative unit that combines SAP system components providing one or more services. The services provided by an application server are started or stopped together.

An instance profile is used to set the parameters of all the components of an application server. Each application server has its own shared memory segment or buffer areas in RAM. A single SAP system may have multiple application server instances.

As the figure above shows, each application server instance runs on a Host. However, multiple application servers can be deployed on a single host. Each application server is identified by the (three-character) SAP system ID (SID) of the system to which it belongs and a unique (two-digit) instance number.

At the time of installation, the first application server instance installed is called Primary Application Server (PAS). Each additional application server instance installed for that SAP system is called an Additional Application Server (AAS).

Each SAP system also provides centralized services deployed on a separate application server instance. This instance is known as the "ABAP Central Services Instance" and is often abbreviated as "ASCS instance".

The SAP runtime system consists of a large number of parallel processes that work together. Watch the following video to learn about the processes that make up an SAP application server.

You can now define ABAP platform architecture and the processes and functions of an application server instance.