Migration and Hybrid

Mainframe Migration - Moving Legacy Systems to the Cloud with AWS Mainframe Modernization

Learn about mainframe cloud migration using AWS Mainframe Modernization. This article covers two migration patterns - replatforming (Micro Focus) and refactoring (Blu Age) - along with migration strategies.

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Challenges of Mainframe Migration

Mainframes have supported core business operations at financial institutions, insurance companies, and government agencies for decades, but high licensing costs, a shortage of specialized talent, and technological obsolescence have become serious challenges. The mainframe-specific technology stack, including millions of lines of COBOL code, CICS and IMS transaction processing, and JCL batch processing, raises the bar for cloud migration. AWS Mainframe Modernization is a service dedicated to migrating mainframe workloads to the cloud, offering two migration patterns: replatforming and refactoring.

Two Migration Patterns

The replatforming pattern uses the Micro Focus (now OpenText) runtime to run COBOL/PL/I code on AWS with minimal changes. Compatible runtimes for CICS, IMS, and JCL are provided, requiring minimal application code modifications. Migration is faster and lower risk, but the benefits of cloud-native architecture (serverless, microservices) are limited. The refactoring pattern uses Blu Age tools to automatically convert COBOL/PL/I code to Java. The converted code runs as Spring Boot-based microservices and can be deployed on ECS/EKS. While the migration timeline is longer, it modernizes the architecture to cloud-native, improving long-term maintainability and extensibility. Both patterns are provided as managed runtime environments, so AWS handles runtime installation, patching, and scaling.

Testing and Phased Migration

The Application Testing feature automatically compares outputs from the same inputs between the pre-migration mainframe and the post-migration AWS environment, verifying functional equivalence. It compares batch processing output files, transaction processing responses, and database states, generating detailed reports when differences are found. A common phased migration strategy starts by moving development and test environments to the cloud, followed by batch processing, and finally online transaction processing. Setting up a parallel operation period between the mainframe and cloud and gradually switching traffic minimizes risk. Integration with DMS (Database Migration Service) also supports data migration from mainframe databases (DB2, VSAM) to RDS or DynamoDB. To learn best practices for legacy modernization, related books on Amazon can be helpful.

Mainframe Modernization Pricing

The refactoring pattern (Blu Age) is priced based on the number of code lines to be converted, with individual quotes from the AWS account team. The replatforming pattern (Micro Focus) uses hourly billing for the managed runtime, at approximately $0.355/hour for an m5.large equivalent. With either pattern, post-migration AWS infrastructure costs are significantly lower than annual mainframe operating costs. Use Migration Evaluator to analyze the TCO of your current environment and compare it with post-migration cost estimates for investment decisions.

Summary - Guidelines for Using Mainframe Modernization

AWS Mainframe Modernization is a service dedicated to migrating mainframe workloads to the cloud. It offers two patterns - replatforming (minimal changes for rapid migration) and refactoring (converting to Java for cloud-native modernization) - letting organizations choose a migration strategy that fits their requirements. Application Testing for equivalence verification and a phased migration approach minimize migration risk. It's well-suited for organizations looking to reduce mainframe costs and modernize their technology stack.

Related Services

AWS Mainframe ModernizationA service that helps migrate and modernize mainframe applications to AWSAWS Database Migration ServiceA fully managed migration service that moves databases to AWS with minimal downtimeAWS Migration HubA service that centrally manages progress across multiple migration tools and visualizes the entire migration project

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