As they describe here AWS has launched a mainframe migration competency, to help companies ditch their mainframes.
Some useful resources for further information include Patterns and Best Practices and AWS Partner Network (APN) Blog – Mainframe section.
Speaking at Re:invent 2018 Phil De Valance of AWS offers a detailed overview of what’s involved in migrating these older systems: ‘Mainframe Modernization with AWS: Patterns and Best Practices‘.
From 08:30 he describes the patterns they have as a toolbox for modernizing to AWS and divides them into two main families; one of which deals with shutting down of mainframes (Short-term Migration) and the other which adds functionality to the mainframe (Augmentation).
Short-term Migration include emulator rehosting, automated refactoring and re-platforming for Linux, where the customer could benefit from the AWS services like Elastic Load Balancing, Auto Scaling, Amazon RDS Database, Amazon CloudWatch Monitoring.
From 22:38 he explores the Augmentation scenario, which includes replicating mainframe data to AWS so that services like data analytics can be applied, and new digital channel capabilities like mobile can be developed.