F.7.2.2.3 Service Class Provider
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##### F.7.2.2.3 Service Class Provider

The N-SET operation allows the SCU to request that the SCP update selected Attribute values for a specific Modality Performed Procedure Step SOP Instance. This operation shall be invoked through the use of the DIMSE N-SET Service used in conjunction with the appropriate Modality Performed Procedure Step SOP Instance. The N-SET value for Specific Character Set (0008,0005) does not replace the previous value. The SCP shall appropriately modify its internal representation so that subsequent operations reflect the combination of the character sets in use by the Attributes in this N-SET and those used by Attributes that have not been modified.

### Note

The SCP may need to convert the text for instance to the Unicode character set. If the SCP is not able to perform a necessary conversion it may return the Invalid Attribute value error code (0106H).

The SCP shall return, via the N-SET response primitive, the N-SET Response Status Code applicable to the associated request. Contingent on the N-SET Response Status, the SCP shall update the Referenced Performed Procedure Step Attributes.

The SCP shall accept N-SET request primitives only if the value of the already existing Attribute "Performed Procedure Step Status" (0040,0252) is "IN PROGRESS". If the already existing Performed Procedure Step Status Attribute has another value, the SCP shall set the failure status code "Processing failure" (Code: 0110H) with a Specific Error Comment (see Section F.7.2.2.4).

The SCP may itself modify any Attributes of the Modality Performed Procedure Step SOP Instance only after the "Performed Procedure Step Status" (0040,0252) has been set to "COMPLETED" or "DISCONTINUED".

### Note

1. Such coercion of Attributes by the SCP may be necessary to correct, for example, patient identification information or incorrectly selected scheduling information. Such an operation is not permitted to the SCU by the requirements described in Table F.7.2-1, which might create a new Modality Performed Procedure Step SOP Instance to achieve the same objective.

2. Under exceptional circumstances, it may be necessary for the SCP to itself set the Performed Procedure Step Status (0040,0252) to COMPLETED or DISCONTINUED, for example if the Modality has failed. When the Modality recovers, subsequent N-SETs may fail.

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