Senior Mainframe Assembler Developer (HLASM / z/OS)

Senior Mainframe Assembler Developer (HLASM / z/OS) Project Details - Location: Central & Eastern Europe - Workload: Full-time - Duration: Long-term Rate: $23–25/hour (B2B) We are looking for an experienced Senior Mainframe Assembler Developer to join a long-term project focused on developing, optimizing, and maintaining low-level applications within an IBM mainframe environment. The role requires deep expertise in HLASM, IBM z/OS, system-level debugging, and performance optimization. Responsibilities - Develop, maintain, and optimize Mainframe Assembler (HLASM) code. - Analyze complex system requirements and implement reliable low-level solutions. - Debug production issues, analyze system dumps, and resolve critical incidents. - Optimize application performance, memory usage, and I/O operations. - Integrate Assembler modules with COBOL, PL/I, and Java applications. - Work with IBM mainframe technologies, including z/OS, CICS, IMS, and DB2. - Troubleshoot system-level issues using IPCS, SYSUDUMP, and specialized debugging tools. - Collaborate with technical teams and stakeholders to ensure system stability. - Participate in code reviews, technical documentation, mentoring, and knowledge transfer. Requirements - 7–10+ years of professional Assembler development experience, including at least 5 years working with mainframe systems. - Strong hands-on expertise in HLASM (High Level Assembler). - Deep understanding of IBM mainframe architecture, instruction sets, and macros. - Strong experience with IBM z/OS, MVS, CICS, IMS, and DB2. - Knowledge of VSAM, GDGs, and JCL. - Understanding of memory management, I/O operations, and interrupt handling. - Experience with low-level debugging and dump analysis using IPCS and SYSUDUMP. - Familiarity with IBM Debug Tool, Abend-AID, OMEGAMON, or Fault Analyzer. - Experience integrating Assembler modules with COBOL, PL/I, or Java. - Understanding of APIs, MQ messaging, and middleware. - Strong analytical, troubleshooting, and problem-solving skills. - Good communication skills and experience supporting knowledge transfer. Nice to Have - IBM Certified System Programmer certification. - IBM z/OS Mastery certifications. - Experience mentoring other mainframe developers. If you have extensive hands-on HLASM expertise and enjoy solving complex system-level challenges within IBM mainframe environments, we'd be happy to hear from you!