The format of requests is defined by the TP monitor. It includes a standard header, which is the same for all applications that use the TP monitor, and a request body, which is defined by the application.
The TP monitor does the rest: it compiles forms definitions and does run-time translation of each form into a request.
(Certain requests can only be issued from terminals in a guarded area, such as a money transfer room.) Since the OS does not know about request types, and DBMSs typically do not know the terminal from which requests originate, this function must be performed in the TP monitor.
To reduce load, the TP monitor can deactivate terminals by stopping the processes connected to those terminals.
More often, they are implemented by the TP monitor or OS.
If threads are implemented by the TP monitor, the OS regards the service call as a call from a process, not from a thread.
If multithreading is implemented by the TP monitor, one must create multiple (perhaps multithreaded) processes to get this physical concurrency.
Thsi approach is used in IBM's CICS TP monitor, using SNA LU6.2 $(10$).
Remote procedure call (RPC) is a mechanism, implemented by the OS or TP monitor, that makes message passing look like procedure calls [7].