Services
Mainframe modernization services: moving COBOL and z/OS workloads in controlled steps
We assess your batch and online workloads, then move them off the mainframe, or around it, one piece at a time, with tests around current behavior and rollback points.
- COBOL, JCL, CICS and DB2 workloads
- Tests that capture current behavior first
- Retain, wrap or migrate, decided per workload
Mainframe modernization means changing how workloads written for z/OS are run, maintained and integrated. It rarely means moving everything. A typical estate has COBOL programs, JCL batch chains, CICS transactions and DB2 or VSAM data, and each part may take a different path.
Some workloads move to Java or C# in the cloud. Some run on emulation or a managed runtime. Some stay on the mainframe and gain APIs. The aim is a plan that matches each workload to the right option, based on evidence from the code, the batch schedule and the data. Our COBOL modernization page covers the code side in more detail.
How we move a mainframe workload
The same loop repeats for each workload.
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Map the estate
Programs, copybooks, JCL, schedules, data sets and interfaces are inventoried and linked.
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Record behavior
Characterization tests capture current outputs for real inputs, including awkward edge cases.
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Choose a pattern
Each workload is placed on a path: retain, rehost, replatform, refactor or retire.
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Migrate a slice
One batch job or transaction moves first and runs alongside the original, with outputs compared.
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Cut over by stages
Traffic and batch windows move in phases, with rollback points, until the mainframe workload can stop.
Typical mainframe problems we are asked about
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Batch windows that keep growing
Overnight jobs run into business hours, and nobody is sure which steps can run in parallel.
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Knowledge held by few people
The COBOL and JCL are understood by a small group, and the documentation is thin.
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Opaque business rules
Logic is spread across copybooks, JCL and stored procedures with no single description.
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Costly change
Small changes need long test cycles because there are no automated tests.
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Tight coupling to data
VSAM and DB2 structures are shared by many programs, so moving one piece affects many.
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Integration limits
Other systems depend on file transfers and message queues that are hard to change.
Rehost, refactor or retain
Rehost or emulate
Moves COBOL to a compatible runtime on other infrastructure with few code changes. It is quicker and keeps behavior close, but you still maintain COBOL.
Refactor to Java or C#
Converts code to a mainstream language so more engineers can work on it. Automated translation tends to mirror the original structure, so expect review and cleanup.
Retain and wrap
Leaves stable programs in place and exposes them through APIs. Often the lowest-risk first step, though the mainframe and its costs remain. AWS offers a mainframe modernization service with refactor and replatform patterns, covered on our AWS mainframe modernization page.
Mainframes run high volumes with mature tooling, and matching that elsewhere takes design and load testing. Batch ordering, character encodings, packed decimal arithmetic and rounding rules are common sources of subtle differences. Parallel runs find them. Parallel runs also take effort.
We cannot promise cost savings, a date or zero downtime. Whether leaving the mainframe saves money depends on licensing, volumes and what you must keep. Incremental migration reduces risk and cannot remove it. Your compliance obligations continue throughout, and your auditors set the controls.
Mainframe questions we hear most
Do we have to leave the mainframe completely?
No. Many organizations move some workloads and keep others. Stable, high-volume programs may be better wrapped with APIs, while reporting or new features move out. We assess each workload and recommend retain, rehost, refactor or retire, including the case where doing little is the right answer.
How do you avoid changing business behavior?
We write characterization tests before touching code. They record current outputs for real or representative inputs. Migrated code must reproduce them, and a parallel run compares results again on live data. Differences are investigated rather than ignored, including rounding and date handling.
Can you convert COBOL to Java automatically?
Tools exist that translate COBOL to Java or C#, and we may use them where they fit. The output usually needs review, testing and restructuring to be maintainable. Translation alone does not tell you whether behavior matches, so tests and comparison remain essential.
What about data on DB2 and VSAM?
Data moves with its own plan: schema mapping, character set conversion, reconciliation counts and a sync period while both systems are live. Data often takes longer than code, so we assess it early, test with realistic volumes and reconcile totals before any cutover.
Is there a mutual NDA before you see our code?
Yes. A mutual NDA can be signed before any code or data is shared, and we can start from a description of the estate. Work then follows your own security controls and compliance obligations. Please do not send credentials or source code in the first request.
Describe your mainframe estate
Use the request form or message us on WhatsApp. A rough description of the workloads is enough to begin.
What to send
- Languages such as COBOL, PL/I or Assembler
- Subsystems such as CICS, IMS and batch
- Data stores such as DB2, VSAM or IMS DB
- Rough program count or lines of code
- Cloud target and timing
Plan the move before you commit to it
Request a code audit for a written assessment and phased roadmap for your mainframe workloads.