The N-ACTION procedures are initiated by the invoking DIMSE-service-user issuing an N-ACTION request primitive. On receipt of the N-ACTION request primitive the DIMSE-N protocol machine shall:
⎯ construct a Message conveying the N-ACTION-RQ
send the Message using the P-DATA request service (See 8.1)
On receipt of a Message conveying an N-ACTION-RQ the DIMSE-N protocol machine shall issue an N-ACTION indication primitive to the performing DIMSE-service-user.
On receipt of the N-ACTION response primitive, issued by the performing DIMSE-service-user, the DIMSE-N protocol machine shall:
⎯ construct a Message conveying the N-ACTION-RSP
⎯ send the Message using the P-DATA request service (See 8.1)
On receipt of a Message conveying an N-ACTION-RSP the DIMSE-N protocol machine shall issue an N-ACTION confirmation primitive to the invoking DIMSE-service-user, thus completing the N-ACTION procedure.
The performing DIMSE-service-user may return an N-ACTION-RSP with the status of Failed or Refused before the complete N-ACTION-RQ request Message has been completely transmitted by the invoking DIMSE-service-user (this is called an early failed response). Upon receipt of this Failed or Refused N-ACTION-RSP the invoking DIMSE-service-user may terminate the Message before it is completely sent (i.e. set the Last Fragment bit to 1 in a Data PDV for this Message, see Annex F). Following this, it may invoke another operation or notification. It is a protocol violation for an invoking DIMSE-service-user to set the Last Fragment bit to 1 before an N-ACTION-RQ Message has been completely transmitted if it has not received a Failed or Refused N-ACTION-RSP to that request.
Note: When an Association is operating in asynchronous mode, it is possible for an invoking DIMSE-service-user to transmit several Messages before a response. Therefore, while sending a Message it may receive a response to a previously transmitted Message. In this case this response is not an early failed response because the related Message has already been sent.