The term “AS/400” often appears in job descriptions as a historical reference, creating confusion for those unfamiliar with its decades-long history in enterprise computing. This experience refers to a specialized skill set centered on a highly stable, integrated business platform used by companies worldwide. Understanding what AS/400 experience entails and why it remains a sought-after skill is important for navigating career opportunities. The platform continues to power mission-critical operations across major industries, making professionals who can manage and modernize it extremely valuable.
Understanding the IBM i Platform
The Application System/400 (AS/400) was an IBM mid-range computer system introduced in 1988. It succeeded the System/36 and System/38 platforms. Over the years, the system underwent several rebrands, including the eServer iSeries and System i, before merging into the IBM Power Systems product line in 2008. Today, the hardware is part of the IBM Power Systems family, and the operating system is officially known as IBM i, an evolution of the original OS/400.
Despite the official name changes, “AS/400” remains the common term used by the community and hiring managers. The platform is distinguished by its unique architecture, which integrates the operating system, a relational database (DB2 for i), and system security into a single, object-based environment. This integrated design provides stability and ease of administration. The IBM i operating system continues to evolve, supporting modern technologies like virtualization and cloud integration while maintaining backward compatibility with older applications.
Why This Legacy Experience Still Matters
The longevity of the IBM i platform is due to its reputation for stability, security, and reliability in handling core business processes. The platform is known for high availability, often achieving near 100% uptime, which is required for organizations that cannot tolerate service interruptions. Its sophisticated, built-in security model is integrated directly into the operating system, making it resilient against threats.
Companies in finance, manufacturing, logistics, retail, and healthcare rely on the IBM i because their decades-old Enterprise Resource Planning (ERP) and core banking systems are built upon it. Replacing these customized applications would be a costly undertaking. Professionals with AS/400 experience are responsible for systems that manage billions in transactions and inventory, acting as custodians of mission-critical business logic.
The platform’s design contributes to a lower total cost of ownership (TCO) because it requires minimal supervision from IT administrators compared to other enterprise systems. This allows a smaller team of skilled IBM i professionals to manage complex systems. Demand is driven by the need to maintain, modernize, and integrate these core systems with newer technologies like cloud services, ensuring business continuity.
Technical Skills Defining AS/400 Experience
The technical knowledge defining AS/400 experience is specific, encompassing programming, database management, and system control. Proficiency in these areas allows professionals to develop applications, manage data, and maintain system health.
Programming Languages
The foundation of AS/400 application development rests heavily on the Report Program Generator (RPG) language. Modern experience requires knowledge of RPG IV, specifically the Integrated Language Environment (ILE) for modular programming, and the free-format syntax for a modern coding style. The Control Language (CL) is necessary for writing system-level programs, automating tasks, and executing system commands. While RPG and CL are primary, skills in COBOL or modern open-source languages like Java, Python, and PHP are increasingly valued for integration and modernization projects.
Database Management and SQL
The integrated database, known as DB2 for i, requires experience working directly with its structure and manipulation tools. Professionals must be able to manage data structures using Data Description Specifications (DDS) for defining files, although this method is being superseded. Proficiency in Structured Query Language (SQL) is important for writing complex queries, creating stored procedures, and optimizing data access within DB2. The ability to integrate SQL with embedded RPG code is a high-demand skill for modern application development.
System Operations and Control
System operations experience focuses on the administration and health of the IBM i environment. This includes managing job queues to ensure efficient batch processes and handling security profiles to control user access. Professionals must be adept at using the traditional 5250 terminal emulation, often called the “green screen,” to execute CL commands and monitor system performance. Administrative tasks also cover managing backup and recovery procedures and ensuring the system is configured for high availability and disaster recovery.
Common Roles for AS/400 Professionals
The specialized nature of the platform leads to several distinct professional roles that require AS/400 experience. These roles generally fall into development, administration, or a combination of both, supporting the entire application lifecycle.
IBM i Developer
An IBM i Developer, often still called an AS/400 Programmer, focuses on creating, maintaining, and enhancing business applications. This role requires coding in RPG (especially modern free-format) and CL, debugging programs, and integrating the core system with newer applications using APIs and web services. Developers translate business requirements into functional code and ensure software reliability.
AS/400 Administrator or System Operator
This role is responsible for the overall infrastructure and operational stability of the server. Their work involves system performance tuning, managing security settings and user profiles, installing software, and overseeing system upgrades and patches. Administrators troubleshoot system-level issues and ensure data backup and recovery processes are sound.
Business Analyst
A Business Analyst with AS/400 experience serves as a bridge between the technical team and business stakeholders. This professional uses their understanding of the system’s capabilities and data structures to gather requirements, analyze business processes, and communicate system changes. They are instrumental in modernization projects.
Developing and Advancing Your AS/400 Career
A career path in the IBM i ecosystem requires a commitment to continuous modernization of skills. The most effective way to gain foundational knowledge is through formal training, such as official IBM courses or community-driven educational programs, which often provide access to sandbox environments for hands-on practice.
Career advancement is driven by embracing modern development tools and techniques. Learning free-form RPG, mastering SQL for complex data manipulation, and utilizing Integrated Development Environments (IDEs) like Rational Developer for i (RDi) are necessary steps. Integrating the IBM i with external systems using web services, APIs, and open-source languages ensures professionals can connect the platform’s core logic to the rest of the enterprise IT landscape. This blend of deep system knowledge and modern integration capability positions professionals for leadership roles in modernization and system architecture.