Mainframe z/OS Administrator – Contract – Office Based We are seeking a Senior Mainframe z/OS Administrator / Systems Programmer to join a large enterprise environment supporting critical IBM Z infrastructure. This is a hands-on role focused on z/OS system administration, upgrades, performance tuning and disaster recovery within a 24/7 production estate. Key Responsibilities * Plan and execute z/OS upgrades, maintenance, PTFs and APARs * Install, configure and support ISV products (Broadcom/CA, BMC, Rocket Software) * Manage IBM Z hardware including CPC, LPAR configuration, HMC/SE, IOCP/IODF * Monitor and tune performance using RMF, SMF, TMON, SAS, WLM * Support GDPS, IPL testing and disaster recovery execution * Provide incident resolution and participate in on-call support Essential Skills * Strong hands-on experience with z/OS installation, configuration and support * Proven experience delivering major z/OS upgrades * Deep knowledge of LPAR, HMC, IOCP, IODF, FICON, OSA, Coupling Facility * Experience supporting ISV tools (Broadcom, BMC, Rocket) * Performance tuning and capacity management expertise Desirable * GDPS exposure * Automation tools such as OPS/MVS or System Automation * Experience within large enterprise or regulated environments This role is ideal for a Senior z/OS Systems Programmer / Mainframe Infrastructure Engineer who thrives in complex, mission-critical environments and owns delivery from upgrade planning through to DR execution. Apply now to discuss full details and day rate