DICOM PS3.18 2019a - Web Services
6.9.5.3.2 Response Headers

If the User-Agent specifies a Procedure Step State (0074,1000) attribute with a value of "CANCELED" and the UPS Instance is already in that state, the response message shall include the following HTTP Warning header field:

If the User-Agent specifies a Procedure Step State (0074,1000) attribute with a value of "COMPLETED" and the UPS Instance is already in that state, the response message shall include the following HTTP Warning header field:

If the request was rejected with an HTTP 409 status code, the response message shall include one of following messages in the HTTP Warning header field describing the nature of the conflict:

DICOM PS3.18 2019a - Web Services