IBM i Knowledge Base
IBM i is the operating system that runs on IBM Power Systems. This section covers how it works, how it's licensed, its roadmap, and what IBM i support looks like today.
IBM i (formerly OS/400, then i5/OS) is one of the most resilient operating systems in enterprise computing. This section explains what IBM i is, how it differs from AS400 as a term, and what the current IBM i roadmap means for your organization.
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IBM i Licensing Explained
IBM i licensing is tied to the processor tier of the underlying IBM Power hardware, not just to core count or user seats. Understanding software tiers, program license terms, and how licensing carries across a hardware upgrade is essential before budgeting a Power Systems project.
IBM i Modernization Options
Modernizing IBM i almost never means leaving the platform. The real options fall into five categories: interface modernization, API enablement, cloud integration, database modernization, and application modernization, each addressing a different pain point without a rip-and-replace migration.
IBM i Operating System Explained
Beyond the definition, IBM i works differently under the hood than Windows, Linux, or UNIX: work management runs through subsystems and jobs, changes are applied through PTFs, and system startup follows an IPL rather than a simple reboot. This is how it actually operates day to day.
IBM i Release History
From OS/400 V1R1 in 1988 through IBM i 7.5 today, the IBM i version lineage spans nearly four decades under three different names. This is the release timeline, from the original AS400 operating system to the current version.
IBM i Roadmap
IBM has continued to invest in IBM i through regular OS releases, Technology Refreshes between major versions, and certification on each new Power Systems generation, most recently Power11. This is what that pattern of investment looks like and what it signals for planning purposes.
IBM i Security Basics
IBM i has a strong security reputation built into its object-based architecture, but that reputation has led many organizations to under-invest in configuration. Security levels, user profiles, object authorities, and exit points are the core concepts worth understanding.
IBM i Support Status
IBM publishes fixed end-of-support dates for each IBM i release. IBM i 7.3 support ended in April 2026; IBM i 7.4 is supported through April 2028 and IBM i 7.5 through April 2030. Knowing where a specific release stands is the first step in any support or upgrade planning conversation.
What Is IBM i?
IBM i is the operating system that runs on IBM Power Systems hardware. It is the direct software descendant of OS/400, the operating system IBM shipped with the original AS400 in 1988, and it still runs applications written for that platform decades ago.