DURATION: 3 months initial contract
LOCATION: Edinburgh, Manchester, Leeds OR Halifax (2 days to local office)
WORKING HOURS: Monday to Friday, standard business hours plus participation in a 24/7 on-call rota
ONSITE REQUIREMENTS: Hybrid working with 2 days per week onsite at local office
LEGAL RIGHT TO WORK: Candidates must have the legal right to work in the UK. Sponsorship is not available for this role.
Atrium Global is supporting a major financial services client in the appointment of an experienced Mainframe Assembler Engineer to join a critical heritage engineering team supporting enterprise banking platforms and core transactional systems.
JOB OVERVIEW
We are seeking a highly experienced Mainframe Assembler Engineer with strong IBM z/OS expertise to support and enhance mission‑critical banking systems. The role combines operational BAU support, incident resolution, technical change delivery and platform modernisation across a complex mainframe estate.
You will work across HLASM, CICS, IBM MQ and core z/OS technologies, supporting high‑availability systems and contributing to transformation initiatives within a regulated enterprise environment.
This role includes participation in out-of-hours deployments and a 24/7 on‑call support rota.
RESPONSIBILITIES
- Provide technical support for IBM High Level Assembler applications within a z/OS environment
- Support and troubleshoot CICS and IBM MQ integrated services
- Perform root cause analysis for incidents, abends and performance issues across production and non‑production environments
- Develop, maintain and enhance Assembler code for planned releases and platform improvements
- Maintain and optimise JCL batch processing and transaction performance
- Support upgrades, migrations and infrastructure changes across the mainframe estate
- Collaborate with COBOL, DB2 and infrastructure teams to deliver integrated technical solutions
- Participate in release validation, deployment readiness and production support activities
- Ensure adherence to ITIL governance, operational standards and risk controls
- Contribute to technical documentation, design reviews and continuous improvement initiatives
REQUIREMENTS
- Proven experience supporting and developing IBM High Level Assembler (HLASM) on z/OS
- Strong hands‑on knowledge of CICS, IBM MQ, JCL and VSAM
- Experience troubleshooting incidents and abends within enterprise mainframe environments
- Familiarity with tools such as Abend-Aid, IPCS, Omegamon or File‑Aid
- Experience supporting both BAU operations and project delivery activities
- Understanding of COBOL and DB2 integration within mainframe platforms
- Knowledge of MQ security, TLS and operational governance controls
- Experience with automation or scripting tools such as REXX, Shell, Ansible or UrbanCode
- Strong analytical and problem‑solving skills within high‑availability environments
- Excellent communication and stakeholder collaboration skills
NICE TO HAVE
- Experience within financial services or highly regulated enterprise environments
- Exposure to modernisation or transformation programmes involving legacy systems
- Previous experience working within large‑scale enterprise banking platforms
