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AWS mainframe modernization

AWS mainframe modernization, from assessment to staged cutover

We assess your workloads, help you choose replatform or refactor for each, and run the move to AWS in steps, with testing against the live mainframe and a rollback plan.

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  • Workload inventory and pattern choice first
  • Data, batch and online tested in parallel
  • Runs inside your cloud and security controls

What is AWS mainframe modernization?

AWS offers a managed service and reference approaches for moving mainframe workloads onto its cloud. The two main patterns are replatform, where existing programs run largely as they are on a managed runtime, and refactor, where code is converted into modern services. Which pattern fits depends on the workload, not on the vendor.

The service is one piece of a project. You still need an inventory of what runs on the mainframe, a plan for data and batch scheduling, test evidence that results match, and a cutover plan. That is the work we do. We plan and run the migration with your engineers, inside your own AWS account and security model.

For the broader picture of options beyond AWS, read our mainframe modernization page. If you are still deciding whether to move at all, a cloud readiness assessment comes first.

How a mainframe to AWS move is run

The stages are the same for most estates. The time each takes is not, and we do not estimate it without a review.

  1. Assess the portfolio

    We inventory applications, programs, jobs, data stores and interfaces, and group them by complexity, business criticality and coupling.

  2. Choose a pattern per application

    Each group is placed in retain, replatform, refactor or retire. The reasons and tradeoffs are written down for your stakeholders.

  3. Build a landing zone and test bed

    Accounts, networking, identity, logging and encryption are set up to your rules, and a test environment is loaded with representative data.

  4. Migrate data and batch

    Data is converted and synchronized. Batch chains are rebuilt on a scheduler with the same dependencies, restarts and timing.

  5. Parallel run and cutover

    Outputs from both environments are compared. Workloads move in stages, and the mainframe stays available until each stage proves stable.

Replatform or refactor on AWS

ReplatformRefactor
Code Mostly unchanged COBOLConverted to Java or C#
Speed to exit Usually quickerUsually slower
Long-term skills COBOL skills still neededMainstream developer skills
Test effort Runtime and data behaviorEvery converted function
Flexibility later Limited until refactoredHigher once stabilized

What has to be designed, not just moved

These are the areas where mainframe migrations to AWS commonly need extra planning.

  • Batch windows

    Nightly jobs have strict order and restart rules. They must run in the same sequence and finish in the same window on the new platform.

  • Transaction integrity

    Online transactions rely on mainframe commit and recovery behavior. The replacement design must give equal consistency guarantees to the business.

  • Data conversion

    Encodings, packed decimals and file formats need conversion and validation, and sometimes a move from hierarchical to relational storage.

  • Security and audit

    Access control, logging and encryption are built to your policies and reviewed by your own security and audit teams.

  • Interfaces

    Partners and internal systems connect through queues, files and protocols that have to keep working or be replaced together.

  • Operations

    Monitoring, backup, disaster recovery and on-call procedures must exist and be rehearsed before the mainframe is retired.

Risks and limits

Moving to AWS does not remove complexity. It changes who manages it. Cost depends on workloads, data volume and design, and running both environments in parallel adds cost for a period. We do not predict savings and we do not promise a date.

  • Some workloads are better left on the mainframe, or wrapped with APIs, because the risk of moving them outweighs the benefit.
  • Performance of a given job on the new platform must be measured, not assumed.
  • Product features and service names change over time, so we confirm details against current documentation at the start of each project.

Your auditors and regulators define compliance requirements. Our work aligns to them and does not substitute for your own reviews.

Mainframe to AWS questions

Should we replatform or refactor?

Replatform is usually faster and carries less change, but it keeps the old code and skills dependency. Refactor costs more up front and gives a codebase that mainstream developers can maintain. Many programs mix both, deciding per application after the portfolio assessment.

Can the mainframe and AWS run together during migration?

Yes, and this is the normal approach. Data synchronization and API routing let some workloads run in AWS while others remain on the mainframe. This reduces risk, since you can move back, but it needs careful design of data ownership at every stage.

Do you work in our AWS account?

Yes. The environment belongs to you, uses your identity and network controls, and follows your security reviews. We prefer to build with infrastructure as code so that your teams can read, review and reproduce everything we set up, and so that the setup does not depend on any one of our engineers.

What does the first engagement look like?

Usually an assessment, which produces an inventory, pattern recommendations and a phased roadmap you can take to your own stakeholders. It can be run as a fixed-scope legacy code audit. You decide afterward whether to continue with us, and the roadmap is yours either way.

Start with a conversation

Tell us what runs on the mainframe and what the move has to achieve. Message us on WhatsApp at +92 326 5200333 or use the request form. A mutual NDA can be signed before you share anything.

What to send

  • Applications and their business criticality
  • Languages, middleware and databases in use
  • Rough capacity and batch volumes
  • Cloud constraints: region, account, security
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Please do not send secrets, source code or production data in the first message.

Considering a mainframe move to AWS?

Send the request form or message us on WhatsApp with the workloads, volumes and your cloud constraints.

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