When a TP encounters an error in its processing or cannot grant a requested confirmation, the TP can call the Send_Error service to notify its partner. A TP can call Send_Error from Send or Receive state. The partner receives notice of the error by return code on its next call to APPC/MVS.

If the TP that detects the error is in Send-pending state (has just received data and send control on the same call), the TP needs to specify where it found the error: in data that it received from the partner or in data it was preparing to send. To do so, specify a value of receive_error or send_error in the error_direction parameter of the Send_Error service.