7.2 A-RELEASE service

The graceful release of an association between two AEs shall be performed through ACSE A-RELEASE request, indication, response, and confirmation primitives. The initiator of the service is hereafter called a requestor and the service-user which receives the A-RELEASE indication is hereafter called the acceptor. It shall be a confirmed service.

Figure 7-2 illustrates the graceful release of an association between two AEs.

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Figure 7-2ASSOCIATION RELEASE

7.2.1 A-RELEASE PARAMETERS

Table 7-4 lists the parameters for the A-RELEASE service which shall contain fixed values or shall not be used by DICOM Application Entities in this standard.

Table 7-4A-RELEASE SERVICE PARAMETERS

A-RELEASE parameter name Request Indication Response Confirmation
reason UF UF(=) UF UF(=)
user information NU NU(=) NU NU(=)
result MF MF(=)

7.2.1.1 Reason (fixed)

When used on the request primitive, this parameter identifies the general level of urgency of the request. This parameter shall always use the value “normal” in this standard.

7.2.1.2 Result (fixed)

This parameter shall always take the value “affirmative” in this standard.

7.2.2 A-RELEASE SERVICE PROCEDURE

7.2.2.1 An UL service-user that desires to release the association shall issue an A-RELEASE request primitive. This requestor shall not issue any further primitives other than an A-ABORT request primitive until it receives an A-RELEASE confirmation primitive.

Note: Even though the requestor of the A-RELEASE service shall not issue any further primitive other than A-ABORT, it may receive P-DATA Indication primitives.

7.2.2.2 The UL service-provider shall issue an A-RELEASE indication primitive to the acceptor. The acceptor then shall not issue any UL primitives other than an A-RELEASE response primitive, an A-ABORT request primitive, or P-DATA Request primitive.

7.2.2.3 To complete the A-RELEASE service, the acceptor shall reply to the A-RELEASE indication primitive by issuing an A-RELEASE response primitive. An accepting DICOM Application Entity shall always issue an A-RELEASE response primitive with an “affirmative” result parameter (i.e. accept the release).

7.2.2.4 After an A-RELEASE response has been issued, the acceptor shall not issue any further primitives for the association thereafter, including P-DATA Requests.

7.2.2.5 The UL service-provider shall issue an A-RELEASE confirmation primitive always with an “affirmative” value for the Result parameter.

7.2.2.6 A requestor in either AE may disrupt the A-RELEASE service procedure by issuing an A-ABORT request. When the acceptor receives an A-ABORT indication, the association is released with the possible loss of information in transit.

7.2.2.7 An A-RELEASE service procedure collision results when requestors in both AEs simultaneously issue an A-RELEASE service primitive. In this situation, both UL service-users receive an unexpected A-RELEASE indication primitive. The following sequence shall occur to complete the normal release of the association:

a) The association-requestor shall issue an A-RELEASE response primitive.

b) The association-acceptor waits for an A-RELEASE confirmation primitive from its peer. When it receives one, it shall then issue an A-RELEASE response primitive.

c) The association-requestor receives an A-RELEASE confirmation primitive.

The association shall be released when both ACSE service-users have received an A-RELEASE confirmation primitive.