The distinction between system programmer and system administrator varies widely among mainframe sites. In smaller IT organizations, where one person might be called upon to perform several roles, the terms may be used interchangeably.

In larger IT organizations with multiple departments, the job responsibilities tend to be more clearly separated. System administrators perform more of the day-to-day tasks related to maintaining the critical business data that resides on the mainframe, while the system programmer focuses on maintaining the system itself. One reason for the separation of duties is to comply with auditing procedures, which often require that no one person in the IT organization be allowed to have unlimited access to sensitive data or resources. Examples of system administrators include the database administrator (DBA) and the security administrator.

While system programmer expertise lies mainly in the mainframe hardware and software areas, system administrators are more likely to have experience with the applications. They often interface directly with the application programmers and end users to make sure that the administrative aspects of the applications are met. These roles are not necessarily unique to the mainframe environment, but they are key to its smooth operation nonetheless.

In larger IT organizations, the system administrator maintains the system software environment for business purposes, including the day-to-day maintenance of systems to keep them running smoothly. For example, the database administrator must ensure the integrity of, and efficient access to, the data that is stored in the database management systems.

Other examples of common system administrator tasks can include:

• Installing software
• Adding and deleting users and maintaining user profiles
• Maintaining security resource access lists
• Managing storage devices and printers
• Managing networks and connectivity
• Monitoring system performance

In matters of problem determination, the system administrator generally relies on the software vendor support center personnel to diagnose problems, read dumps, and identify corrections for cases in which these tasks aren't performed by the system programmer.