In a mainframe IT organization, the system programmer (or systems programmer) plays a central role. The system programmer installs, customizes, and maintains the operating system, and also installs or upgrades products that run on the system.

The system programmer might be presented with the latest version of the operating system to upgrade the existing systems. Or, the installation might be as simple as upgrading a single program, such as a sort application.

The system programmer performs such tasks as the following:

• Planning hardware and software system upgrades and changes in configuration
• Training system operators and application programmers
• Automating operations
• Capacity planning
• Running installation jobs and scripts
• Performing installation-specific customization tasks
• Integration-testing the new products with existing applications and user procedures
• System-wide performance tuning to meet required levels of service

The system programmer must be skilled at debugging problems with system software. These problems are often captured in a copy of the computer's memory contents called a dump , which the system produces in response to a failing software product, user job, or transaction. Armed with a dump and specialized debugging tools, the system programmer can determine where the components have failed. When the error has occurred in a software product, the system programmer works directly with the software vendor's support representatives to discover whether the problem's cause is known and whether a patch is available.

System programmers are needed to install and maintain the middleware on the mainframe, such as database management systems, online transaction processing systems and Web servers. Middleware is a software "layer" between the operating system and the end user or end user application. It supplies major functions that are not provided by the operating system. Major middleware products such as DB2®, CICS®, and IMS™ can be as complex as the operating system itself, if not more so.