# IBM Mainframe Assembler

JPID: DLTJP00062218

Skill: IBM Mainframe Assembler

No. of Positions: 02

Experience Range: Relevant experience – 5–7 Years (3 Years Hands-on Mainframe Assembler)

Rates: 25 LPA Max

Work Location: Hyderabad / Bangalore / Chennai / Pune

Rounds of Interview: 2 Rounds

Mode of Interview: Virtual

Work Timing: 12 PM–9 PM

Work Mode: Hybrid

## Must-to-Have Skills

- HL Assembler.
- Hands-on experience on Assembler.
- 3 years of hands-on experience on Assembler.
- Mainframe Modernization.
- COBOL.

##

We are seeking a highly experienced Mainframe Assembler Practitioner with deep expertise in IBM z/OS Assembler (HLASM) and strong hands-on capability to rewrite assembler programs into COBOL, validate functional equivalence, fix defects identified during testing, and optimize performance. The role also requires the ability to analyze and document complex assembler logic, translating low-level technical constructs into clear functional and business-oriented documentation.

### 1. Assembler Code Analysis & Understanding

- Analyze complex IBM z/OS Assembler (HLASM) programs, macros, and control blocks to fully understand:
- Business logic and functional flows.
- Data structures, register usage, and storage management.
- Control flow patterns (branching, looping, error handling).
- Perform call chain and dependency analysis, including interactions with:
- COBOL programs.
- CICS/Batch environments.
- Databases (DB2, VSAM, IAM, Datacom).
- Utility and system services.
- Identify and document implicit business rules embedded in assembler logic, including edge cases and exception handling.

### 2. Assembler to COBOL Rewrite

- Rewrite assembler programs into functionally equivalent COBOL code, ensuring:
- Logical equivalence with original assembler behavior.
- Compliance with enterprise COBOL standards.
- Maintainable, readable, and modular COBOL structures.
- Translate low-level assembler constructs (register operations, bit manipulation, packed/zoned decimal handling) into appropriate COBOL constructs.
- Handle conversion of:
- Batch programs.
- CICS online programs.
- Utility and interface modules.
- Work closely with automated or semi-automated rewrite tooling where applicable, validating and refining generated code.

### 3. Testing & Validation





- Design and execute unit and integration test cases to validate COBOL code against original assembler behavior.
- Support mainframe comparison testing where original assembler acts as the system of record for validation, a common pattern in complex rewrite programs.
- Analyze test failures by:
- Comparing assembler logic, extracted business rules, and rewritten COBOL code.
- Identifying functional mismatches, data handling issues, and boundary condition errors.
- Iteratively fix defects in rewritten COBOL code and retest until functional equivalence is proven.

### 4. Performance Optimization

- Analyze performance-critical assembler code paths, including:
- CPU-intensive loops.
- I/O-heavy operations.
- Storage and memory utilization patterns.
- Optimize assembler or rewritten COBOL code by:
- Reducing instruction count or inefficient branching.
- Improving data access patterns.
- Minimizing unnecessary I/O or storage operations.
- Ensure that rewritten COBOL meets or exceeds original assembler performance benchmarks where required.

### 5. Functional & Technical Documentation

- Produce clear, structured documentation describing:
- Program purpose and high-level business functionality.
- Detailed logic flow and decision points.
- Input/output structures and file/database interactions.
- Translate assembler-level technical details into language consumable by functional analysts, testers, and downstream developers.
- Document assumptions, limitations, and known edge cases uncovered during analysis and rewrite.

### 6. Collaboration & Governance

- Collaborate with:
- Architects, testers, and modernization leads.
- Automation, tooling, and QA teams.
- Participate in design reviews, code walkthroughs, and defect triage sessions.
- Adhere to enterprise governance standards for code quality, documentation, and testing artifacts.

## Required Skills & Experience

### Core Technical Skills

- 10 years of hands-on experience with IBM z/OS Assembler (HLASM).
- Strong expertise in COBOL (Enterprise COBOL)



on z/OS.
- Deep understanding of:
- z/OS execution model.
- Register usage and storage management.
- Assembler macros and copybooks.
- Experience with Batch and CICS environments.
- Solid knowledge of mainframe data technologies:
- VSAM, IAM.
- DB2 and/or Datacom.

### Rewrite & Testing Expertise

- Proven experience in assembler-to-COBOL rewrites, preferably in large modernization programs.
- Solid debugging skills across assembler and COBOL.
- Experience designing and executing test strategies for legacy rewrites.
- Ability to reason about behavioral equivalence, not just syntactic conversion.

### Performance & Quality

- Demonstrated ability to analyze and optimize performance-critical mainframe code.
- Strong attention to detail and root cause analysis skills.

### Documentation & Communication

- Ability to document complex low-level logic in a clear and structured manner.
- Strong written and verbal communication skills.
- Comfortable explaining assembler logic to non-assembler practitioners.

### Preferred Qualifications

- Experience with modernization or migration programs (e.g., Mainframe → Modern platforms).
- Exposure to automated rewrite or mining tools.
- Experience working in regulated or mission-critical enterprise environments (insurance, banking, life sciences).

## What Success Looks Like in This Role

- Assembler logic is accurately understood, documented, and preserved.
- Rewritten COBOL code is functionally equivalent, well tested, and performant.
- Defects are quickly identified, resolved, and validated.
- Program knowledge is no longer tribal and is captured in durable documentation.

## Additional Must-to-Have Skills

- 6–9 years of hands-on experience in Mainframe Assembler (z/OS) development.
- Strong understanding of JCL and mainframe debugging tools (e.g., IPCS, Abend-AID).
- Working experience of Assembler and COBOL.
- Proven ability to analyze complex system logic and optimize for performance.
- Familiarity with batch and online transaction processing environments.
- A problem-solving mindset with meticulous attention to detail.
- Excellent communication skills to collaborate across technical and business teams.

Pay: Up to ₹2,500,000.00 per year

Work Location: Hybrid remote in Pune, Maharashtra

📌 IBM Mainframe Assembler - HL Assembler (Pune)
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