The scheduler provided by the NAP component takes complete control of scheduling all applications running in the system. It is fully preemptive, and allows several processes to run concurrently. Only the current foreground process is permitted to write to the screen.
The entry point provided by the 3270 emulator on the CMDGoTSR call is executed as a fully independent background thread of execution. Scheduling between the foreground application's thread and the emulator background thread occurs in response to: