Protected subsystems have many applications, from databases to common system management situations.

One use for a protected subsystem might be a group membership list that you want to make available to all group members. The list contains the names, addresses, personnel numbers, and interests of group members. When the membership list is set up as a protected subsystem, all members of the group can read selected information and update specific types of information.

A protected subsystem might also solve the problem of confidential information being sent to printers in public areas. You could write an application to filter data for sensitive information. Confidential files would be sent to printers in restricted areas, while public files would be sent to any available printer. Any user with execute access to the application could use the restricted printers, but only through the protected subsystem.