The Architecture Shift: From R/3 to S/4HANA

For many years, SAP followed a three-tier architecture with presentation, application, and database layers where the choice of database did not matter at all, Oracle, DB2, SQL Server, or MaxDB would suffice under the ABAP application server. In contrast, SAP S/4HANA deliberately breaks such abstraction. Only SAP HANA can be used as a database, and this constraint allows an entirely new rearchitecting of how ABAP programs will be coded, compiled, and executed.

As a result of the old R/3 model, ABAP was constrained to bring entire sets of data from the database into application layer memory ("fat SELECT"), process them using internal ABAP tables, and then store results back in the database. This round trip was the main performance issue. S/4HANA closes that gap by moving processing logic to HANA in-memory column store, the famous code-to-data approach.

The ABAP Application Server & Runtime Stack

The AS ABAP (Application Server ABAP) continues to be the primary runtime environment for S/4HANA. The AS ABAP consists of a multi-process system that runs on the Linux operating system and consists of several major components working together to execute ABAP applications: