Section: 6.3.9 UDR discovery and selection
Content: Multiple instances of UDR may be deployed, each one storing specific data or providing service to a specific set of NF consumers as described in clause 4.2.5. In segmented UDR deployment, different instances of UDR store the data for different Data Sets and Data Subsets or for different users. A UDR instance can also store application data that applies on any UE, i.e. all subscribers of the PLMN. If the NF service consumer performs discovery and selection, the NF consumer shall utilize the NRF to discover the appropriate UDR instance(s) unless UDR instance information is available by other means, e.g. locally configured on NF consumer. The UDR selection function in NF consumers is applicable to both 3GPP access and non-3GPP access. The NF consumer or the SCP shall select a UDR instance that contains relevant information for the NF consumer, e.g. UDM/SCP selects a UDR instance that contains subscription data, while NEF/SCP (when used to access data for exposure) selects a UDR that contains data for exposure; or PCF/SCP selects a UDR that contains Policy Data and/or Application Data. The UDR selection function in UDR NF consumers considers the Data Set Identifier of the data to be managed in UDR (see UDR service definition in clause 5.2.12 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]). Additionally, the UDR selection function in UDR NF consumers should consider one of the following factors when available to the UDR NF consumer when selecting a UDR that stores the required Data Set(s) and Data Subset(s): 1. UDR Group ID the UE's SUPI belongs to. 2. SUPI; e.g. the UDR NF consumer selects a UDR instance based on the SUPI range the UE's SUPI belongs to or based on the results of a discovery procedure with NRF using the UE's SUPI as input for UDR discovery. 3. GPSI or External Group ID; e.g. UDR NF consumers select a UDR instance based on the GPSI or External Group ID range the UE's GPSI or External Group ID belongs to or based on the results of a discovery procedure with NRF using the UE's GPSI or External Group ID as input for UDR discovery. 4. UDR capability to store application data that is applicable on any UE (i.e. all subscribers of the PLMN). In the case of delegated discovery and selection, the NF consumer shall include the available factors in the request towards SCP.