AS400 Modernization: Choose What to Change First
Improve the part of an AS400 or IBM i environment that is holding the business back without replacing parts that still work.
Start with the business problem, not a demand to leave IBM i. The right move may be a better screen, an API, cleaner database access, a cloud connection, an application change, or a planned migration.
Choose What to Modernize
- Improve the user experience without replacing the application
- Connect AS400 applications to websites, mobile tools, and other systems
- Connect IBM i to cloud services while keeping the core workload
- Improve Db2 for i access, reporting, and data use
- Update RPG applications and reduce maintenance risk
- Compare modernization with staying put or migrating
Articles in This Hub
AS400 API Integration
Exposing existing RPG and COBOL program logic through APIs lets an AS400 or IBM i system connect to mobile apps, e-commerce platforms, and partner systems without rewriting decades of business logic. This is usually the highest-leverage modernization step an IBM i shop can take.
AS400 Application Modernization
Application modernization, refactoring RPG into free-format ILE code, modularizing monolithic programs, and introducing new languages alongside existing logic, is the broadest and highest-risk modernization category. It is also the one most often confused with a full migration, when the goal is almost always to extend the application's life, not replace it.
AS400 Cloud Integration
IBM i does not run on general-purpose public cloud infrastructure, but that does not mean AS400 environments are cut off from cloud services. Backup and disaster recovery, hybrid application architectures, and IBM's own Power-based cloud hosting are all realistic paths.
AS400 Database Modernization
Many AS400 databases still rely on decades-old DDS-described physical and logical files. Converting them to modern SQL-defined DB2 for i tables and views unlocks standard tooling, better performance options, and easier integration, without requiring a database migration to a different platform.
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.
AS400 Modernization Explained
AS400 modernization means updating how an IBM i environment looks, connects, and is built, not replacing the platform underneath it. Understanding the five modernization categories, and picking the right one for the actual problem, is the difference between a focused project and an over-scoped migration.
Green Screen Modernization
Replacing the 5250 green screen interface is usually the first modernization step organizations take, because it is visible, relatively low-risk, and does not require touching the underlying RPG or COBOL logic. Screen wrapping, rehosting, and native web front ends are the three main approaches.
When Not to Migrate Off AS400: Modernize, Replace, or Stay
Do not migrate off AS400 because the name sounds old. Compare the business logic, reliability, integration needs, replacement fit, and total cost before deciding whether to modernize or move.