Technology Overview
The SAP ABAP Platform is the core application server and development environment used to build, run, and manage business-critical applications in SAP systems such as SAP S/4HANA. It provides a complete runtime, development model, and infrastructure for developing both standard and custom business logic using the ABAP programming language.
The ABAP Platform is built as a classic three-tier setup:
- Presentation layer: SAP GUI, Fiori Launchpad, SAP Business Client; the front-end where users interact with the system.
- Application (Server) layer: Where ABAP code executes, transaction processing, business rules, communication. Multiple application server instances may exist, identified by a System Identifier (SID) and instance number.
- Database layer: The persistent store for all ABAP data. For S/4HANA underlying database is SAP HANA. For ERP systems you can find different database technologies (DB2/LUW, Oracle, MS-SQL…).
Client: In SAP, a “client” refers to a logical partition of the SAP system that is used to separate data and configuration settings for different departments, organizations or subsidiaries within a company. Each client has its own set of master data, transactional data, and customizing settings.
Instance: An “instance” refers to a physical installation of the SAP software and associated database on a server. One SAP instance can support multiple clients, but each client can only reside in one instance.
In summary, a client is a logical partition within an SAP system and an instance is a physical installation of the SAP software.
For each SAP instance:
- Separate directories are defined on the OS
- Shared file systems can be used
- Entries are created in operating system configuration files (/etc/services, /etc/sapconfig…)
- Communication entries are created in the host
- Start and system profiles are created
- Operating system users and groups are added