SAP S/4HANA is one of the leading ERP systems and is used by many companies worldwide. The architecture of SAP S/4HANA is based on a client-server architecture with three process levels: the presentation level, the application level and the database level. In addition to the database level, the SAP HANA platform also offers extensive functionalities on the application level and should therefore by no means be regarded exclusively as a database platform.

The various services of the ABAP platform are grouped into instances. The platform consists of at least two instances: the Central Services Instance (ASCS) and the Primary Application Server (PAS).


The PAS instance and the AAS instances allow users to log in and access the application. The logon is done by logging into the system. Depending on the technology used, the ABAP dispatcher or the ICM is responsible for connecting to the system.

The PAS instance is an important component in an SAP system because it is responsible for managing the system landscape and provides various services. It enables users to access the applications in the system by connecting to the dispatcher or ICM.


There is only one instance of ASCS (ABAP System Central Services) in the system.

This instance houses essential and central components that operate across instance boundaries.

The components located in the ASCS instance include the enqueue server and the message server.

Optionally, an RFC gateway and an SAP Web Dispatcher can also be present in the ASCS instance.

Enqueue Server

The Enqueue Server is used to manage locks and releases of critical SAP objects, thus ensuring data consistency and integrity in the system. The Message Server, on the other hand, enables communication between different SAP systems and components, thus ensuring a smooth exchange of information within the system.


The RFC Gateway is an optional component that acts as an interface between SAP systems and external applications. It enables communication between different systems, regardless of whether they are based on SAP technology or not. SAP Web Dispatcher, on the other hand, is an optional component that manages traffic between the Internet and SAP systems. It facilitates the scaling of SAP systems and ensures even load distribution across different servers.

In summary, the components running in the ASCS instance are of central importance for the smooth functioning of the SAP system. They ensure high data consistency and integrity, provide seamless communication inside and outside the system, and enable efficient scaling and load balancing.


The ICM (Internet Communication Manager) is a component responsible for managing communication between SAP systems and the Internet. It ensures that requests sent to the SAP system over the Internet are processed correctly and that data is transferred securely. The PAS always includes an ABAP dispatcher and a number of work processes managed by the dispatcher.

ABAP Dispatcher

The ABAP Dispatcher is a component responsible for distributing requests to the various SAP systems. It connects the users to the respective AAS instance that runs the requested applications.

Additional application servers (AAS) can be added to further scale at the application level, besides the ASCS and PAS instance.


The architecture of SAP S/4HANA includes several instances, including the primary PAS instance and optional AAS instances. Here are some important points to note:

  • AAS instances are optional and serve as a complement to the primary PAS instance.
  • They provide a scalable way to increase the number of users that can access the application simultaneously.
  • Each AAS instance consists of the same components as the PAS instance and allows users to log in and access the application.
  • The message server of the ASCS instance ensures that requests from users are distributed among the available servers to ensure optimal performance.

There are three possible builds of an SAP S/4HANA system, all of which include instances of the SAP ABAP platform at the application level:

  • From a software perspective, the ABAP platform provides only the basic technical functions of the system.
  • Administrators can also manage other SAP software products on the ABAP platform.
  • It is important to understand that the ABAP platform provides only the basic technical functions of the system, and other application-level products are required.

In summary, the ABAP platform is a central component of the application layer within the architecture of SAP S/4HANA.