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 closed. AWS's document history records closure of the Managed Runtime Environment from 7 November 2025 and the Self-Managed Experience from 30 July 2026. The latter change was announced on 30 June 2026. Existing customers can continue using the service. The current overview points new customers toward vendor-direct offerings and AWS Transform, and recommends migration partners or AWS Professional Services for project delivery. These pages were checked on 1 October 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.