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:

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:

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.