An IDMS Mainframe job involves working with IDMS (Integrated Database Management System), a network-based database management system used on IBM mainframes. Professionals in this role handle database administration, performance tuning, application development, and support for IDMS-based systems. They ensure data integrity, optimize queries, and maintain system availability. Skills in COBOL, JCL, ADS/O, and IDMS schema design are often required. These jobs are common in industries like banking, insurance, and government, where legacy mainframe systems are still widely used.