Senior Mainframe Systems Engineer

Job Summary: We are looking for a Senior Mainframe Systems Engineer with strong hands-on experience in IBM z/OS and HLASM. The role focuses on low-level systems tooling, runtime and subsystem environments, module-level development, subsystem exits, and diagnostics rather than application development. Responsibilities Develop and maintain HLASM code running within z/OS runtime and subsystem environments. Build and package modules and analyze load modules. Work with VSAM, QSAM, and Language Environment at the control-block level. Develop and install subsystem exits for CICS, Db2, IMS, or MQ. Use JCL and REXX to automate build, installation, and verification activities. Troubleshoot system dumps and abends using appropriate z/OS diagnostic tools. Analyze module behavior and demonstrate that changes are behavior-neutral before release. Collaborate with infrastructure, application, and security teams on low-level system changes. Required Skills & Qualifications 7-10 years of relevant mainframe

experience, with strong hands-on experience in IBM z/OS. Significant experience working below the application layer in z/OS environments. Strong HLASM/High Level Assembler experience is required; COBOL or PL/I experience alone is not a substitute. Strong knowledge of Binder and Linkage Editor. Working knowledge of Language Environment internals. Experience with VSAM/QSAM control blocks. Knowledge of the z/OS authorization model, including APF and authorized concatenations. Strong JCL and REXX experience. Experience with dump and abend analysis using IPCS, SLIP, GTF, or component trace. Preferred Skills Db2 language interface internals. CICS Global User Exits and threadsafety. IMS DL/I or MQ internals. SMP/E. z/OS trace and diagnostic tooling. IBM Z certifications.