Assess a mainframe application portfolio using code analysis and dependency mapping to classify migration candidates.
Information & Communications Technology
Legacy Mainframe Modernisation and Application Rehosting
Assess legacy mainframe estates and plan a modernisation path, rehosting, re-platforming or refactoring, that migrates COBOL applications and batch workloads with controlled risk.
🗓️Duration5 training days
📚Content4 modules · 8 sessions
🎓On completionAccredited attendance certificate
About the programme
Course Overview
Many core business systems still run as COBOL applications on mainframes that were never designed for cloud integration, yet carry decades of business logic that nobody wants to rewrite from a blank page. Replacing them outright is expensive; leaving them untouched accumulates cost as mainframe skills and capacity become scarce. This course teaches participants to assess a mainframe estate using code analysis and dependency mapping tools, and to choose between rehosting, re-platforming, refactoring, rearchitecting or replacing each application based on its business value and technical condition. Participants plan the migration of batch workloads defined in job control language, translate or emulate transaction processing, and design a data migration path from indexed file structures and relational mainframe databases to modern database platforms. Sessions cover the strangler fig pattern for incrementally routing transactions away from the mainframe, dual-run validation that compares outputs before cutover, and rollback planning for a phased migration. A case exercise works through selecting a modernisation strategy for a payment-processing application and designing a parallel run that proves a new platform matches legacy behaviour. By the end, participants can build a modernisation roadmap, sequence migration waves and manage the risk of a live cutover.
Expected Learning Outcomes
Select a modernisation strategy, rehost, re-platform, refactor, rearchitect or replace, for each application based on value and risk.
Plan the migration of batch workloads and their scheduling dependencies to a target platform.
Design a data migration path from indexed and relational mainframe data structures to modern database schemas.
Apply the strangler fig pattern to route transactions incrementally away from a mainframe application.
Design dual-run validation that compares legacy and modernised outputs before a production cutover.
Plan rollback and contingency procedures for a phased mainframe migration wave.
Who Should Attend
Enterprise architects planning a mainframe modernisation or exit strategy.
Application managers responsible for ageing COBOL or transaction-processing systems.
Migration project leads coordinating mainframe-to-cloud or mainframe-to-midrange moves.
Infrastructure engineers assessing rehosting platforms for mainframe workloads.
Data engineers planning migration of legacy mainframe data to modern databases.
IT risk managers evaluating cutover and rollback plans for legacy system replacement.
Course Modules
Select any module to see its sessions and points.
01Assessing the Mainframe Estate
2 sessions · 8 points
Session 1Portfolio Analysis and Dependency Mapping
- Inventory mainframe applications, batch jobs and interfaces to establish the full scope of the modernisation estate.
- Use static code analysis tools to measure COBOL programme complexity, duplication and dead code before migration.
- Map data and transaction dependencies between applications to identify migration waves that can move independently.
- Classify applications by business value and technical condition to prioritise which systems to modernise first.
Session 2Choosing a Modernisation Strategy
- Compare rehosting, re-platforming, refactoring, rearchitecting and replacing against each application's risk profile.
- Estimate the cost and timeline difference between an emulation-based rehost and a full application rewrite.
- Identify applications where the underlying business logic is undocumented and requires reverse engineering first.
- Build a business case that links modernisation strategy choice to expected cost, risk and delivery timeline.
02Migrating Batch and Transaction Processing
2 sessions · 8 points
Session 1Batch Workload Migration
- Translate batch job steps and scheduling dependencies into an equivalent workflow on the target platform.
- Rebuild batch job scheduling and restart logic so failure recovery matches existing operational expectations.
- Validate that migrated batch jobs produce output files and reports identical to the legacy runs.
- Coordinate batch migration sequencing with dependent downstream jobs to avoid breaking overnight processing chains.
Session 2Transaction Processing Modernisation
- Assess transaction volumes and response time requirements before selecting an emulation or rewrite approach.
- Map screen-based transactions to equivalent application programming interfaces or modern user interfaces.
- Preserve transaction integrity and recovery behaviour when migrating to a target transaction platform.
- Test migrated transactions under representative peak load before scheduling a production cutover.
03Data Migration and the Strangler Fig Pattern
2 sessions · 8 points
Session 1Migrating Mainframe Data Structures
- Map indexed and relational mainframe data structures to modern schemas while preserving referential integrity.
- Design extract, transform and load pipelines that migrate historical data without disrupting live processing.
- Reconcile migrated data against source records using automated comparison to catch transformation errors.
- Plan incremental data synchronisation for applications that must run on both platforms during transition.
Session 2Incremental Migration with the Strangler Fig Pattern
- Apply the strangler fig pattern to route selected transaction types to a modernised service while others remain on the mainframe.
- Build a routing layer that directs traffic between legacy and modernised components during the transition period.
- Sequence which transaction types to strangle first based on business risk and technical complexity.
- Monitor both legacy and modernised paths during transition to detect discrepancies before full cutover.
04Cutover, Validation and Decommissioning
2 sessions · 8 points
Session 1Dual-Run Validation
- Design a dual-run period where legacy and modernised systems process the same transactions in parallel.
- Compare outputs from both systems automatically to identify discrepancies before committing to the new platform.
- Define acceptance criteria and sign-off thresholds that must be met before a dual-run period can end.
- Investigate and resolve discrepancies found during dual-run without extending the validation period indefinitely.
Session 2Cutover and Decommissioning
- Plan a cutover sequence and rollback trigger criteria for each migration wave before go-live.
- Coordinate cutover communication with business users, support teams and downstream system owners.
- Decommission legacy components only after retention and audit requirements for historical data are satisfied.
- Capture lessons learned from each migration wave to refine the approach for subsequent waves.
What the participant receives
4 course modules
A structured syllabus
8 training sessions
across 5 days
32 detailed points
Applied, detailed content
Accredited attendance certificate
On completing the programme
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