About Us (Ensono) Ensono is an expert technology adviser and managed service provider. As a relentless ally, we accelerate clients’ digital transformation to achieve business outcomes that stand to last. Our dedicated team helps organizations optimize today’s systems across any hybrid environment with services such as consulting, mainframe and application modernization, public cloud migration and cloud-native development. With certified experts in AWS, Azure and Google Cloud and recognized as Microsoft Datacenter Transformation Partner of the Year, Ensono has over 3500+ associates globally and is headquartered in greater Chicago. We care about your success, offering comprehensive strategic and managed services for mission-critical applications. Our Advisory and Consulting services can help upfront with an application strategy or find the right places for your applications – whether it’s public, multi or hybrid cloud, or mainframe. And because we span across all mission-critical platforms, we can meet you wherever you are in your digital transformation journey, with 24/7 support when you need it. We are your relentless ally, flexing with you when challenges emerge so you don’t feel stuck in place. With cross-platform certifications and decades of experience, our technology experts have become an extension of your team so you’re continuously innovating – doing more with less while remaining secure. And that’s just the beginning. Senior z/OS Base System Engineer Your role: As a Senior z/OS Base System Engineer, you will act as a key technical leader in maintaining and advancing our core mainframe operating system environment. We’re looking for an experienced z/OS Systems Software Engineer to: design, develop, and improve the core digital platform services we provide on z/OS. You will apply a broad range of software engineering practices, from analyzing system needs and developing new features to automated testing and deployment. You’ll ensure the quality, security, reliability, and compliance of our operating system solutions by implementing both functional and non-functional requirements. You’ll help build observability into our systems, monitor production health, resolve incidents, and perform root-cause analysis to improve stability. In addition, you will monitor and optimize Parallel Sysplex and Coupling Facility configurations, ensuring high availability across mainframe clusters. As a senior engineer, you will make critical technical decisions and articulate your solution designs and proposals to stakeholders and technical leadership, serving as a trusted advisor on mainframe systems architecture. You will also share knowledge and expertise with colleagues, mentor junior engineers, and contribute to our engineering culture via code reviews, technical presentations, and participation in internal communities. Your team: In our agile operating model, crews are aligned to larger products and services that fulfill business needs through multiple autonomous pods. You’ll be working in the Mainframe Platform Core Services team, a global crew responsible for mainframe infrastructure services and innovation. You will collaborate closely with other specialized mainframe engineering teams (e.g., DB2 Engineering and Online Systems Engineering for CICS/MQ) to deliver end-to-end reliable solutions. This role involves frequent interaction with operational teams across geographies (such as Switzerland, USA) to ensure alignment of system enhancements and operations. As a senior member, you’ll often interface with lead engineering boards and stakeholders to align mainframe platform improvements with business goals. Your expertise: You have 10+ years’ experience in z/OS systems programming or a similar senior engineering role. Your qualifications include: Deep knowledge of z/OS internals – Expert skills in z/OS operating system architecture, design, and implementation, with mastery of core z/OS components and subsystems. Parallel Sysplex & Coupling Facility mastery – Comprehensive experience in Geographically Dispersed Parallel Sysplex (GDPS) operations and Coupling Facility management to ensure high availability and minimal outages. SMP/E and system installation – Hands-on expertise with SMP/E packaging, installation, and maintenance of z/OS software and operating system; capable of planning and executing complex system upgrades and ensuring OS currency (experience up to z/OS 3.1 preferred). Programming & Scripting – Proficiency in REXX, TSO/ISPF, JCL, and other system programming languages; familiarity with Assembler coding is a plus. Performance & Tools – Strong analytical skills and thorough knowledge of z/OS performance tuning and system utilities; experience with IBM and non-IBM system management tools, monitoring, and problem determination utilities. Problem Management & Support – Proven experience providing Level 3 support for mainframe OS infrastructure, including diagnosing complex system issues and devising permanent solutions. - Independent and Proactive – A self-driven engineer capable of working independently, taking initiative in identifying system improvements, and proactively addressing potential issues or vulnerabilities. - Change Management & Documentation – Good understanding of change management processes, with an ability to write clear system design and architecture documents (e.g., network and system design concept documents) and to guide technical changes from concept through production. - Continuous Learning & Strategic Thinking – Eagerness to learn new technologies and practices, reusing strategic platforms and standards; adept at evaluating options and making long-term architectural decisions that ensure sustainability. - Communication & Leadership – Strong communication skills are essential: fluent English (written and spoken) is mandatory, and German language skills are a plus. You are comfortable presenting complex technical decisions to stakeholders and senior management. You also demonstrate leadership through mentoring and by influencing architecture and engineering best practices across the mainframe community. Shift - UK shift "We are an equal opportunity employer. All qualified applicants will be considered for employment without regard to caste, colour, creed, religion, gender, gender identity, sexual orientation, age, disability, HIV status, or any other status protected by law. Candidates with disabilities who require accommodations during the recruitment process are encouraged to contact our Talent Acquisition team to place a request."

Senior z/OS Systems Programmer

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