Administer and maintain IBM z/OS environments, CICS Transaction Server, and IBM MQ. Perform installations, upgrades, migrations, patching, troubleshooting, performance tuning, security compliance, backup and disaster recovery support. Manage change and incident processes, create technical documentation, and support implementation and recovery planning. Provide technical guidance to junior staff and collaborate with infrastructure, cybersecurity, application, and operations teams to maintain secure, highly available mainframe services.