What Is AS/400 (IBM i)?
Sections: A concise, executive-friendly guide to AS/400 (now IBM i): terminology, strengths, modernization strategies, and cloud options on IBM Power.
By Ximple Team
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8–10 min read
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IBM i / Power Systems
AS/400 vs iSeries vs System i vs IBM i — terminology
IBM has rebranded the original AS/400 system several times. Now it is known as IBM Power Systems. In 2000, AS/400 was called the eServer iSeries. In 2006, it became IBM System I. In 2008, it changed to IBM Power Systems.
Brief history & evolution
The first IBM AS400 computer system emerged in 1988. It consisted of the operating system called the OS/400 and the hardware system called the AS/400. Additionally, the first production had an integrated database and other core functions. Over the years, the AS/400 and OS/400 have seen many upgrades.
Before it came to be, IBM had made a computer using the object-based OS in 1978. It was called System/38. The relational database found is similar to the Db2 we know now. Also, some of its concepts made the AS400 software system run smoothly. In 1983, the company made another computer system called System/36. It used RPGII as the primary programming language, and it was only a file management machine.
In 2000, IBM branded the AS/400 again to eServer iSeries and had the OS/400 operating system. This became a server for running internet businesses. In 2006, the company released the iSystem server which consisted of the i5/OS operating system. It became an alternative for companies that would not run the Windows OS.
In 2008, the company released the Power Systems or IBM Power. It was a combination of i5/OS (now called IBM i) and the Unix (also called AIX) OS. Power Systems has a built-in database called DBMS, DB2/400. Although IBM has rebranded its product over the years, it has retained compatibility. Hence, it is easy to run the initial AS/400 programs in modern Power Systems without an issue. There is hope because IBM updates IBM i every three years.
Core architecture (single-level store, DB2 for i, object model)
The platform features an object-based OS with single-level storage, an integrated relational database (DB2/400), web application and web services servers, and a firmware-based virtualization system noted for efficiency.
Security, reliability & performance
- Stability without frequent reboots; strong security due to the object model.
- Integrated components for secure language/database integration.
- Efficient virtualization and streamlined administration compared with Linux/Windows stacks.
- Lower server sprawl and favorable TCO in many environments.
Common workloads (ERP, EDI, warehousing)
IBM i is widely used for ERP, database management, manufacturing operations, eCommerce, and secure multi-application hosting. Users range from SMBs to large enterprises across industries such as manufacturing and IT.
Modernization options
API & UI modernization (REST, Angular/React, Headless)
Expose core business logic as REST/JSON services and progressively modernize UX with Angular/React front-ends while retaining IBM i for data and processes.
Language evolution (RPG Free, COBOL, Java/.NET interop)
Leverage RPG Free and modern toolchains; integrate with Java or .NET services where it makes sense, while maintaining compatibility with existing programs.
Data & analytics (DB2 for i, replication, lakes)
Use DB2 for i as the system of record while replicating to analytics targets/data lakes for BI, AI, and reporting.
Cloud paths for IBM i
IBM Power Virtual Server (PowerVS)
Run IBM i on IBM Power Virtual Server to gain elasticity while preserving compatibility, with options for managed services.
Managed hosting & hybrid patterns
Adopt managed providers or hybrid models as stepping stones—keep sensitive workloads on-prem while offloading others.
Migration & risk management
Consider business disruption costs when moving off IBM i hardware versus incremental modernization. Evaluate TCO, skills, and integration impacts before full platform shifts.
Common myths about AS/400
Despite perceptions of obsolescence, the platform remains active with modern capabilities, integrated web services, and periodic IBM updates.
FAQ
AS/400 remains reliable in various industries for ERP and database management. Newer use-cases include data storage, Java-based development, eCommerce with web-enabled servers, and collaboration via Notes/Domino.
IBM has rebranded the AS/400 multiple times; today it’s part of IBM Power Systems.
Yes. You’ll find IBM i in both SMB and large enterprises. It supports web-enabled applications and secure multi-tenant workloads.
Explore IBM i Modernization with Ximple
See how API-first UX, EDI, and reporting evolve on IBM i and in the cloud.
