DICOM PS3.4 2022c - Service Class Specifications
C. Prior Record Key and Subsequent Response

If Prior Record Key (0008,041C) is present in the Repository Query Request Identifier, the SCP shall return entity records, continuing with the next record key, that satisfy the Key Attribute matching. The SCP shall return a Failure status code A710 if the value of Prior Record Key (0008,041C) is invalid for identifying an entity determining a point of continuation. See Section C.

For a sequential set of Query transactions with the same Key Attribute Values, and for which each C-FIND Request after the first includes a Prior Record Key (0008,041C) value equal to the last Record Key (0008,041B) in the C-FIND Responses of the prior Query transaction, the SCP shall return the same set of C-FIND Responses as if the entire Query would have been completed in a single transaction. Whether new entities and updates received by the SCP after the time of the initial Query transaction might be included in the C-FIND Responses is implementation specific.


  1. For example, an entity added after the time of the initial Query might be assigned a Record Key (0008,041B) that precedes a Record Key (0008,041B) already sent in a C-FIND Response; that entity will not be returned in the set of Query transactions. However, an added entity whose Record Key (0008,041B) is after the last sent Record Key (0008,041B) may or may not be included in the set of Query transactions; as it was added after the initial Query transaction, the implementation determines whether such a change is included in the responses.

  2. The SCP should not assume that the last Record Key (0008,041B) it sent will be used as the Prior Record Key (0008,041C) in a subsequent transaction. Error conditions may cause the SCU to need to resume from an earlier value.

  3. There is no requirement for the Key Attributes in a Request Identifier to be identical to those in a prior Repository Query transaction, even though the presence of Prior Record Key (0008,041C) implies a continuation of a prior transaction. Each Repository Query transaction is independent. The SCP does not need to retain any state information between Repository Query transactions, although it may include state information in the Record Key (0008,041B).

DICOM PS3.4 2022c - Service Class Specifications