Automotive OEM Exits the Mainframe: COBOL to Java Microservices at 50% Lower Cost

Industry

Automotive (OEM) | Legacy Stack: COBOL / DB2 / JCL (Mainframe) | Target: Java Microservices, Cloud-Native
Sanciti AI Agents: RGEN, CodeGen, TestAI | Orchestrated by: LEGMOD
50% lower migration cost | 30% faster time-to-market | 60% faster requirements extraction | 90%+ test coverage

Client

A major automotive OEM running core manufacturing planning, supply chain coordination, and production scheduling on a decades-old mainframe built on COBOL, DB2, and JCL across multiple production facilities.

Challenge

• Thousands of COBOL programs and JCL batch jobs powering mission-critical manufacturing logic with zero modern documentation. The engineers who wrote the original code had left years ago, and every previous migration assessment stalled because no team could map what the batch programs did without reading COBOL line by line.
• MIPS-based mainframe costs escalating annually while the available COBOL engineering talent shrank in parallel. The cost trajectory made the platform unsustainable within a defined planning horizon.
• Two distinct workload types on the same mainframe: overnight batch processing (JCL jobs for supply chain and production data) and daytime online transactions (operations staff screens). Both required migration without disrupting active production schedules.
• High regression risk in a manufacturing environment where an incorrect schedule, wrong part quantity, or broken supplier workflow would directly impact production lines across facilities.
  
  

Solution: Orchestrated by Sanciti AI LEGMOD

Sanciti AI’s LEGMOD governed the entire mainframe migration, orchestrating RGEN, CodeGen, and TestAI through a wave-based execution with human oversight at every stage.

RGEN: Codebase Comprehension and Requirements Extraction
RGEN ingested the full COBOL codebase, DB2 schemas, and JCL job flows. It reverse-engineered business logic, data dependencies, and processing sequences into a structured, traceable system model. What previously stalled at months of manual COBOL reading was completed 60% faster, replacing tribal knowledge with a documented specification covering every module, batch job, and data flow.

CodeGen: Java Microservices Generation
CodeGen generated modern Java microservices from RGEN’s structured output. Batch processing patterns were translated into scheduled jobs and message queues. Online workloads became REST-based services. All generated code was OWASP/NIST quality-scored with SAST and SCA scans completed before human review.

TestAI: Functional Equivalence Validation
TestAI generated equivalence tests comparing mainframe outputs against modernized Java outputs for every migrated module across both batch and online workloads. Tests ran continuously throughout the migration, achieving 90%+ coverage at first-time delivery across the modernized codebase, catching regressions in real time before they reached production. LEGMOD sequenced migration waves by business criticality and dependency depth, separating batch and online tracks to manage risk independently. Every wave had defined entry and exit criteria with human approval gates. All agent interactions passed through Sanciti AI’s guardrails with complete audit trails.

Results

• 50% lower modernization cost compared to the manual re-platform estimate that had been budgeted for large blended COBOL and Java specialist teams.
• 30% faster time-to-market for new feature delivery. Release cycles that required weeks of COBOL development and manual regression now move through CI/CD pipelines on modern Java microservices.
• 60% faster requirements extraction through RGEN’s automated reverse-engineering of the COBOL codebase, unlocking the migration that had stalled in previous manual attempts.
• 90%+ automated test coverage across the modernized codebase, with functional equivalence validated for both batch and online workloads through TestAI.
  
  

Impact

Mainframe fully decommissioned. MIPS-based costs eliminated. Manufacturing and supply chain systems run on modern Java microservices with CI/CD pipelines and cloud-native infrastructure.

The COBOL talent dependency is removed. The codebase is now accessible to the broader Java engineering market. The complete migration is documented and traceable from legacy COBOL module to modernized service to validated test case.

Sanciti AI agents: RGEN, CodeGen, TestAI. Orchestrated by LEGMOD.