AWS Mainframe Modernization

AWS Mainframe Modernization is AWS's managed service for moving COBOL, PL/I, and Assembler workloads onto AWS, offered in two patterns. Replatform, powered by Rocket Software's Enterprise Suite (formerly Micro Focus), recompiles existing COBOL and PL/I largely unchanged onto AWS infrastructure. Refactor converts the application and its data layer into a Java stack — an Angular front end over an API-driven Java backend — while preserving functional equivalence. Refactor originally ran on the Blu Age automated-conversion engine; as of 2025 those capabilities are folded into AWS Transform for mainframe, AWS's agentic modernization service, which reached general availability in May 2025.

New-customer onboarding to the classic experiences is now closed. The Managed Runtime Environment stopped accepting new customers on 7 November 2025 and the Self-Managed Experience on 30 June 2026. Existing customers are unaffected, but AWS directs new mainframe work to AWS Transform for mainframe and to its Mainframe Migration Competency Partners rather than to the original service. Verified against AWS documentation, August 2026.

AWS publishes a rate card rather than quoting per engagement. The Transform and Blu Age runtime costs $0.31 per AWS CPU core-hour on demand, or $0.155 per vCPU-hour on Fargate. The Rocket Software runtime runs $5.55 per core-hour on demand and the Rocket Developer IDE $2.14 per core-hour. Data replication from z/OS via Precisely is $60 per GB, and Assembler-to-COBOL conversion via mLogica is $2.75 per line. AWS Transform's own analysis, developer, and build tooling carries no separate licence fee beyond the infrastructure it runs on.

Two customer results were presented at AWS re:Invent 2025. Fiserv reported cutting a planned 30-month mainframe refactor to 18 months with a 40% maintainability gain, on an application processing over $10B and 150-200 million transactions a day. BMW reported migrating seven applications in six months, cutting test-case creation from ten days to hours and raising its code-quality score from 2.8 to 4.1.

The service fits enterprises with an existing AWS relationship who want the Refactor or Replatform pattern executed inside AWS's own tooling rather than a systems integrator's proprietary platform. This is a reference profile of the AWS product, not a vendor comparison — the mainframe to AWS migration guide covers the delivery side of that path, and the COBOL migration services guide covers supplier selection without assuming a target platform.