SAP RFC SYSTEM FIELDS documentation, setup help and example usage

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RFC System Fields
When an RFC is made, the system field sy-subrc is initialized in the calling program, or set to the value that is specified in exception handling, just like whenever a function module is called. In addition, every time a function module is called remotely, the system fields for messages ( sy-msgid , sy-msgno , sy-msgty , and
sy-msgv1 to sy-msgv4 ) are initialized in the calling program. If the MESSAGE statement is used to send a message of the type "A", "E", or "X" when a remote function module is executed, the classic exception SYSTEM_FAILURE is raised in the calling program. When the exception is raised, the system fields for messages of both types of exception handling are supplied with the properties of the message.