AS400 Migration Myths
"AS400 is dead," "nobody knows RPG anymore," and "modernizing means migrating" are among the most persistent myths driving unnecessary and expensive AS400 migration decisions. Here is what each claim gets wrong.
Decisions to migrate off AS400 are sometimes driven by genuine business need. Just as often, they are driven by claims that sound true but don't hold up to scrutiny. These are the myths that come up most often, and what the evidence actually shows.
Myth: AS400 Is Dead or Dying
This claim has circulated for roughly three decades, and it has been wrong for all of them. IBM continues to release new Power Systems hardware, most recently Power11 in 2025, and new IBM i OS versions, most recently 7.5 in 2022. See is AS400 still used? for the current installed base. A platform with continuous vendor investment and an active user base spanning over 100,000 organizations is not, by any reasonable definition, dead.
Myth: Nobody Knows RPG Anymore
Finding RPG developers is a genuine, well-documented workforce challenge, but "nobody knows it" overstates the problem. RPG developers exist, IBM i-focused staffing firms and consultancies specialize in the skill, and application modernization work, refactoring code into free-format ILE RPG and modularizing it, makes existing systems substantially easier for newer developers to work with. A skills gap is a real reason to invest in modernization and knowledge transfer; it is a weaker reason to migrate an entire working system.
Myth: Modernizing AS400 Means Migrating Off It
As covered in AS400 modernization explained, the large majority of modernization projects, interface, API, database, and application work, happen while staying on IBM i. Conflating modernization with migration leads organizations to either avoid necessary interface and integration work out of fear it commits them to a full migration, or to scope a modernization project so large it effectively becomes one by accident.
Myth: Migrating Off AS400 Is Always Cheaper Long-Term
Migration projects replace tested, production-proven business logic with newly written code, which introduces defect risk that a stable AS400 application, however old, does not carry. Migration total cost of ownership calculations frequently underestimate the cost of rebuilding decades of edge-case business rules, data conversion, retraining staff, and the transition period where both systems must be maintained. For many organizations, particularly those with heavy custom logic and strong IBM i database reliability, modernization investment produces a better return than migration, though this is workload-specific and should be evaluated case by case rather than assumed either way.