SAP three-tier architecture

 SAP Basis plays a crucial role in establishing and maintaining the technical foundation of SAP systems.¹ At its core, SAP Basis leverages a three-tier client-server architecture, which provides a robust, scalable, and flexible framework for enterprise resource planning (ERP) solutions.² This architecture separates the different functionalities of the system into distinct layers, allowing for better management, performance, and security.³

Here's a detailed breakdown of each layer:

1. Presentation Layer (Client Layer)

This is the user interface layer, responsible for how users interact with the SAP system.⁴ It's the "front-end" that displays information to the user and collects input from them.⁵

• Components:
  • SAP GUI (Graphical User Interface): The traditional desktop application that provides a rich graphical interface for users to access SAP modules and execute transactions.⁶ It's available for various operating systems like Windows, macOS, and Linux.⁷
  • Web-based Interfaces: With the evolution of SAP, web-based access has become increasingly prominent.⁸ This includes:
    • SAP GUI for HTML (WebGUI): A web-based version of the classic SAP GUI, accessible via a web browser.⁹
    • Web Dynpro for ABAP (WDA): A web-based UI technology for developing sophisticated web applications in ABAP.¹⁰
    • SAP Fiori: The latest generation of user experience (UX) for SAP applications.¹¹ Fiori provides a modern, role-based, and intuitive user interface designed for simplicity and ease of use across various devices (desktops, tablets, smartphones).¹²
• Functions:
  • Displays SAP screens and data to the end-user.¹³
  • Receives user input (keyboard entries, mouse clicks).¹⁴
  • Sends user requests to the Application Layer for processing.
  • Receives processed data back from the Application Layer for display.
• Key Characteristics:
  • Installed on individual user machines or accessed via web browsers.¹⁵
  • Focuses on user experience and data visualization.
  • Minimal business logic resides here; its primary role is interaction.

2. Application Layer (Application Server Layer)

This is the heart of the SAP system, where all the business logic and application programs reside and execute.¹⁶ It acts as an intermediary between the Presentation Layer and the Database Layer.¹⁷

• Components:
  • Application Servers: One or more application servers host the SAP application programs and services.¹⁸ These servers contain a set of work processes that handle various types of requests.¹⁹
    • Work Processes: These are the core execution units within an application server. Different types of work processes handle specific tasks:
      • Dialog Work Process (DIA): Processes interactive user requests (e.g., logging in, running transactions, entering data).
      • Update Work Process (UPD): Handles database update requests, ensuring data consistency (e.g., saving a sales order, posting a financial document).
      • Background Work Process (BTC): Executes non-interactive, long-running jobs in the background (e.g., batch programs, reports that run overnight).²⁰
      • Enqueue Work Process (ENQ): Manages logical locks on database objects to prevent data inconsistencies when multiple users access the same data.²¹
      • Spool Work Process (SPO): Manages print requests and formats output for printers.²²
    • Dispatcher: Receives user requests from the Presentation Layer and distributes them efficiently to available work processes on the application server for processing.²³ It ensures load balancing among work processes.
    • Gateway: Enables communication between different SAP systems and also between SAP systems and external non-SAP systems (e.g., RFC calls, external programs).
    • Message Server: Facilitates communication between different application servers within the same SAP system. It also plays a crucial role in load balancing by directing user logons to the application server with the lightest load.
  • ABAP Platform (formerly NetWeaver Application Server ABAP): The runtime environment and programming language (ABAP) for developing and executing SAP business applications.²⁴
• Functions:
  • Executes the business logic and application programs (e.g., calculating prices, processing orders, managing inventory).
  • Processes user requests received from the Presentation Layer.
  • Performs data validation and manipulation.
  • Communicates with the Database Layer to retrieve and store data.
  • Manages user sessions and system resources.
• Key Characteristics:
  • Can be scaled by adding more application servers to handle increased workload.
  • Ensures the efficient and reliable execution of business processes.
  • Provides security features like user authentication and authorization at the application level.²⁵

3. Database Layer (Database Server Layer)

This is the lowest tier of the SAP architecture, responsible for storing and managing all the data of the SAP system.

• Components:
  • Database Management System (DBMS): The software that manages the database.²⁶ SAP supports various relational database management systems (RDBMS) like:
    • SAP HANA: SAP's own in-memory database, which is now the primary database for modern SAP applications like S/4HANA, offering high performance and real-time analytics.²⁷
    • Oracle Database
    • Microsoft SQL Server
    • IBM Db2
    • SAP MaxDB (formerly MySQL)
  • Database Itself: The actual storage where all the data is kept. This includes:
    • Business Data: Transactional data (e.g., sales orders, invoices), master data (e.g., customer details, material masters).²⁸
    • Configuration Data (Customizing Data): Settings and parameters that define how the SAP system behaves for a specific organization.
    • System Data: Data related to the SAP system's operation, logs, and metadata.
    • Program Code: The ABAP programs and other executable code of the SAP applications.
• Functions:
  • Stores and retrieves all types of data required by the SAP system.
  • Ensures data integrity, consistency, and security.²⁹
  • Manages data concurrency (multiple users accessing data simultaneously).
  • Provides backup and recovery mechanisms.
• Key Characteristics:
  • Typically runs on dedicated, powerful server hardware with high storage capacity and fast I/O.
  • Accessed exclusively by the Application Layer; the Presentation Layer does not directly communicate with the database.
  • The performance of this layer is critical for the overall SAP system performance.

Benefits of the Three-Tier Architecture:

• Scalability: Each layer can be scaled independently. If the user load increases, more presentation servers or application servers can be added without affecting the database. Similarly, the database can be scaled separately if data volume grows.
• Flexibility: Different layers can run on different hardware and operating systems, allowing for optimized resource utilization.³⁰
• Maintainability and Modularity: Changes or updates in one layer (e.g., a GUI upgrade) generally do not require significant changes in other layers.³¹ This modularity simplifies maintenance and troubleshooting.
• Security: The separation provides enhanced security. The database is not directly exposed to end-users, and all data access is managed and controlled by the Application Layer.
• Performance: Distributing the workload across three layers optimizes performance.³² The application servers can process requests efficiently, reducing the burden on the database server.
• High Availability: Components within each layer can be made redundant, improving the overall availability and reliability of the SAP system.

In essence, the three-tier architecture in SAP Basis ensures that complex enterprise operations can be handled efficiently, securely, and scalably, making it the backbone of SAP's robust business solutions.