Around 120,000 organizations still run business-critical applications on IBM i. Most intend to modernize, yet few execute — because the two options the industry markets most loudly don't fit the typical shop. Here is how rebuilding, hosting, and complete migration actually compare.
| Rebuild the application | Rent & host the AS/400 | Migrate to standard Java on Linux | |
|---|---|---|---|
| Example | Blue Age and similar | Skytap, IBM Power Virtual Server | Infinite i |
| What it does | Take the application apart and regenerate it, component by component | Rehost the existing IBM i environment in a cloud data center | Migrate the whole application to standard Java on Linux; move DB2/400 data to MySQL |
| Your application code | Rewritten — new language | Unchanged | Recompiled whole — migrated, not rewritten |
| Off IBM Power? | Yes | No — still runs on IBM Power | Yes |
| Runs on | A new Java stack | IBM i on IBM Power (hosted) | Standard Java on Linux — AWS, Azure, or GCP |
| Typical timeline | 3+ years | Weeks (lift-and-shift) | 45–60 days |
| Cost profile | Millions; often $10M+ for large estates | Ongoing rental + IBM licensing | ~50% lower run cost; fixed-scope project |
| IBM licensing | Eliminated | Continues | Eliminated |
| Your RPG/COBOL team | Retrained or replaced while the rebuild runs | Still required | Retained — and freed from RPG as the codebase modernizes |
| Business logic | Re-implemented (full regression risk) | Preserved | Preserved exactly |
| End state | Modern language — but every component is new code to validate and own | Same stack, new location; platform lock-in and the skills crisis remain | Same applications and operations; modern language and infrastructure, off Power |
Produces a fully modern Java codebase. The trade-off is time and risk: multi-year programs, costs that can exceed $10M, and re-implementing and re-verifying decades of business rules from scratch. Best reserved for applications that genuinely need re-architecting.
Fast and low-disruption — your environment runs unchanged in a cloud data center. But it is still IBM i on IBM Power, with the same licensing and the same shrinking skills pool. You change the invoice, not the architecture.
The third path. Your whole application is migrated in one pass — RPG, COBOL, CL, DDS, batch and commands together — onto standard Java on Linux, with DB2/400 data moved to MySQL. Typically 45–60 days at roughly half the run cost. Operations are unchanged and certified against the live system; the codebase your developers inherit is modern.
Petro Peru moved their IBM i workload to AWS — off IBM hardware and IBM licenses, in under two months, for less than the cost of renting AS/400 capacity.
Want the full analysis? Read The Third Path, our white paper on the economics and risk of all three approaches.
Send us a representative slice of your RPG, COBOL, CL, and DDS. In about two weeks we will show it running on the cloud you choose — no license commitment until you have seen it work.
The core platform — recompile RPG, COBOL, CL, and DDS to standard Java on Linux, on AWS, Azure, or GCP. 45–60 days. Half the cost of staying on Power.
Learn about Infinite i →An Infinite i add-on for dynamic runtime modernization — capture live 5250 screens into a JSON model and render them as modern, composable web apps. No rewrite.
Learn about Infinite UI →An Infinite i add-on that migrates DB2 for i (DB2/400) data to MySQL on AWS, Azure, or Google Cloud — with referential integrity fully preserved.
Learn about Infinite DataLink →An Infinite i add-on: a modern VS Code IDE for RPG & ILE COBOL — syntax highlighting, IntelliSense, Git, debugging, and AI assistance. In private beta; GA Q3 2026.
Learn about Infinite Studio →