An application can override any system command simply by including the same command name in the application command table.

In this example, the dialog has overridden both the HELP and TSO commands. During ISPF processing, if you enter HELP, the command is passed to the dialog function in control, which determines the action to be taken. The action specified for the TSO command is NOP, which disables the TSO command. ISPF displays an inactive command message when a NOP action command has been processed.