Description
The Unified Data Repository (UDR) is a critical component within the 5G Core (5GC) Service-Based Architecture (SBA), defined by 3GPP. It acts as a centralized, standardized data storage entity for structured data, decoupling data storage from application logic. The UDR stores various data profiles, including Subscription Data (used by the Unified Data Management, UDM), Policy Data (used by the Policy Control Function, PCF), Application Data (used by Network Exposure Function, NEF), and Structured Data for Network Slicing. Architecturally, the UDR exposes a northbound service-based interface (Nudr) using HTTP/2 and JSON, allowing other Network Functions (NFs) like UDM, PCF, and NEF to access and manage data via standardized API operations such as Nudr_DM (Data Management) and Nudr_DR (Data Repository).
Internally, the UDR organizes data into Data Sets, which are collections of data of a specific type for a given user or service. For example, subscription data for a user is stored in a specific data set. The UDR ensures data consistency, integrity, and availability. It supports operations like Create, Read, Update, Delete, and Query (CRUDQ) on these data sets. The repository is designed to be highly scalable and reliable, often implemented with distributed database technologies to handle the massive data volumes and low-latency access requirements of 5G networks. Its role is purely for storage and retrieval; the application logic (e.g., authentication decisions by UDM) resides in the consumer NFs.
The UDR's implementation enables a clear separation between data storage and data usage logic, which is a key principle of the 5GC SBA. This separation allows for independent scalability of storage and processing functions, simplifies upgrades, and fosters innovation. For instance, the UDM can focus on subscription management logic while relying on the UDR for persistent storage. The UDR also supports network slicing by storing slice-specific subscription and policy data, allowing different slices to have isolated or shared data sets as needed. Furthermore, it facilitates data exposure to authorized third-party applications via the NEF, enabling new service paradigms.
Purpose & Motivation
The UDR was created to address the data fragmentation and siloed storage issues present in previous mobile network generations like 4G EPC. In EPC, data was often stored in dedicated, function-specific repositories (e.g., HSS for subscription, SPR for policy), leading to duplication, inconsistency, and complex integration. The 5G vision required a more agile, cloud-native, and service-oriented core network to support diverse use cases from enhanced mobile broadband to massive IoT and ultra-reliable low-latency communications.
The UDR solves these problems by providing a unified, centralized repository for all structured data in the 5GC. This consolidation eliminates data redundancy, ensures a single source of truth, and simplifies data management operations. It directly supports the 5GC's Service-Based Architecture by offering a standardized data storage service that any authorized network function can consume via APIs. This design is essential for enabling network slicing, as each slice can have its dedicated data profiles stored and managed within the same UDR infrastructure, ensuring isolation and efficient resource utilization. The UDR thus future-proofs the network for data-driven services and flexible service deployment.
Architecture
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (80 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-8, normative work from Rel-15.
In Release 15, the UDR (Unified Data Repository) was newly introduced as a central facility for user data convergence, enabling the storage and management of subscription and policy data in a common, logically unique repository. The release defined its role in separating data from application logic, supporting a layered architecture where network elements like the AMF and UDM access data remotely via standardized interfaces. Specific enhancements included detailing UDR interactions, API error handling, subscription mechanisms, and the support for external application data through defined data models.
- Clarification on UDR TS 23.501CR0061
- Usage of Unified access control in priority mechanisms TS 23.501CR0165
- Update and correction of table for AMF, UDM, UDR, NSSF, UDSF and BSF services TS 23.501CR0363
- Unified Access Control for UE configured for EAB TS 23.501CR0543
- 23.501: AUSF, UDM, UDR Discovery TS 23.501CR0594
- Unified Access Control clarification and triggers TS 23.501CR0660
+ 7 more changes
In Release 16, the UDR function was enhanced with new capabilities for network function discovery and data management. Key additions included support for a UDR NF Group ID for association and selection, a service for mapping IMS Public Identity to HSS Group ID, and the ability to store HTTP Headers. Furthermore, specific application errors were defined, and procedures were corrected, such as the creation of subscriptions by the UDM at the UDR.
- eSBA communication schemas related to UDM and UDR discovery and selection TS 23.501CR0800
- Adding UDR NF Group ID association functionality TS 23.501CR1384
- Unified Access Control with NPN TS 23.501CR1298
- Subscription Segmentation in PCF and UDR TS 23.501CR1366
- NRF use of UDR Group ID Mapping service TS 23.501CR1623
- UDR service for mapping IMS Public Identity to HSS Group ID for HSS selection TS 23.501CR1759
+ 8 more changes
In Release 17, the UDR's capabilities were expanded to support new functions like SOR-AF as a Network Function consumer, features for Time Sensitive Communications (TSC) and Data Collection, Analytics, and Reporting (DCAMP), and the storage of non-subscriber related data. It also introduced enhancements for handling URSP policies from an Application Function (AF) and began supporting HSS as a consumer of UDR services. Furthermore, the release added procedures for UDR restoration notifications and improved subscription management, including the ability to cancel subscriptions upon policy association termination.
- UDR restoration notification TS 29.504CR0174
- SOR-AF as NF consumer of UDR TS 29.504CR0173
- UDR features for TSC and DCAMP TS 29.504CR0178
- UDR application data update to support AF influence on URSP TS 29.519CR0257
- AM Influence UDR models for DCAMP TS 29.519CR0260
- Time Synch data in UDR TS 29.519CR0280
+ 13 more changes
In Release 18, the UDR saw enhancements including support for new features like GMEC and the storage of DNAI-EAS Mappings data subsets. It also introduced capabilities for updating restricted status, storing BDT warning notifications, and allowing the PCF to query with multiple S-NSSAIs. Furthermore, Release 18 completed the HR-SBO functionality, updated procedures for the DCSF, and provided corrections to UDR Restoration procedures over several Nudm services.
- Support of new feature “GMEC” in UDR TS 29.504CR0223
- DNAI-EAS Mappings data subset in the UDR TS 29.504CR0241
- DNAI-EAS Mappings data subset in the UDR TS 29.519CR0453
- Completion of HR-SBO functionality in the UDR TS 29.519CR0512
- Update the procedure to support DCSF get and update the repository data TS 29.562CR0139
- Support of updating restricted status in UDR TS 29.513CR0543
+ 8 more changes
In Release 19, the UDR function was enhanced to support new data types and procedures, including the storage of AF-specific UE identifiers, detailed UE policy delivery outcomes, and Device Identifiers for non-3GPP devices connecting behind a UE. New capabilities were added for features like Multiple Traffic Influence, UP Path Change event outcomes, and the storage of UPU Header Protection capabilities, expanding the UDR's role in user data convergence. Furthermore, updates were made for Ambient IoT data clarification and to introduce mechanisms for data restoration with "anyUE" and UDR rediscovery for Data Migration.
- UDR enhancement supporting Device Identifier of non-3GPP Devices connecting behind a UE/5G-RG TS 23.501CR5547
- Multiple Traffic Influence feature addition in UDR TS 29.504CR0280
- UP Path Change event outcome feature addition in UDR Feature negotiation table TS 29.504CR0293
- Detailed UE Policy Delivery Outcome in the UDR TS 29.504CR0320
- AF Specific UE Identifier storage in UDR TS 29.505CR0536
- Addition of traffic routing outcome request in UP path change event subscription in UDR for future PDU(s) TS 29.519CR0560
+ 14 more changes
Explore further
Broader topics and technologies where UDR plays a role.
Defining Specifications
3GPP specifications that define or reference UDR, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 22.985 vj00 | 3GPP User Data Convergence (UDC) concept | Rel-19 |
| TS 23.203 vj20 | Policy and charging control architecture | Rel-19 |
| TS 23.280 vk10 | Common Architecture for Mission Critical Services | Rel-20 |
| TS 23.335 vj00 | User Data Convergence (UDC) Procedures | Rel-19 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.845 va00 | UDC Evolution Study | Rel-10 |
| TS 23.862 vc00 | Interworking Solutions for Mobile Operators & Data Apps | Rel-12 |
| TS 26.804 vj10 | 5G Media Streaming Extensions Study | Rel-19 |
| TS 26.891 vg00 | Media Distribution Services in 5G System | Rel-16 |
| TR 26.919 vj00 | Study on 5G Conversational Media Handling | Rel-19 |
| TS 28.540 vk10 | 5G Network Resource Model (NRM) Management | Rel-20 |
| TR 28.840 vi10 | Technical Report | Rel-18 |
| TS 29.201 vj00 | RESTful Rx Interface for AF-PC Communication | Rel-19 |
| TS 29.212 vj00 | Gx/Gxx/Sd/St Diameter Protocol | Rel-19 |
| TS 29.213 vj20 | PCC Signalling Flows and QoS Mapping | Rel-19 |
| TS 29.214 vj20 | Policy and Charging Control over Rx | Rel-19 |
| TS 29.215 vj00 | S9 Reference Point Stage 3 Specification | Rel-19 |
| TS 29.335 vj00 | Ud Interface Protocol for UDC (Stage 3) | Rel-19 |
| TS 29.503 vj50 | UDM Service Based Interface Stage 3 | Rel-19 |
| TS 29.504 vj50 | Nudr Service Based Interface Stage 3 Protocol | Rel-19 |
| TS 29.505 vj50 | UDR Service for Subscription Data Usage | Rel-19 |
| TS 29.512 vj40 | 5G Session Management Policy Control Service | Rel-19 |
| TS 29.513 vj40 | 5G PCC Signalling Flows & QoS Mapping | Rel-19 |
| TS 29.514 vj40 | 5G System; Policy Authorization Service; Stage 3 | Rel-19 |
| TS 29.519 vj40 | UDR Usage for Policy & Exposure Data | Rel-19 |
| TS 29.521 vj40 | 5G Binding Support Management Service Stage 3 | Rel-19 |
| TS 29.522 vj40 | 5G NEF Northbound APIs Stage 3 | Rel-19 |
| TS 29.523 vj20 | 5G Policy Control Event Exposure Service | Rel-19 |
| TS 29.525 vj40 | 5G UE Policy Control Service Stage 3 | Rel-19 |
| TS 29.543 vj20 | 5G Data Transfer Policy Control Services Stage 3 | Rel-19 |
| TS 29.554 vj10 | 5G Background Data Transfer Policy Control Service | Rel-19 |
| TS 29.562 vj40 | HSS Services for IMS & GBA Interworking | Rel-19 |
| TS 29.563 vj30 | TS 29563: Nhss services for HSS-UDM interworking | Rel-19 |
| TS 29.808 vg00 | Study on Nudsf Service Based Interface | Rel-16 |
| TS 29.817 vc10 | Study on XML-based Rx interface for PCC | Rel-12 |
| TS 29.866 vj00 | IMS Disaster Prevention & Restoration Enhancement | Rel-19 |
| TS 29.890 vg00 | CT3 5G System Technical Report | Rel-16 |
| TS 32.181 vj00 | User Data Convergence Management Framework | Rel-19 |
| TS 32.182 vj00 | UDC Common Baseline Information Model (CBIM) | Rel-19 |
| TS 32.255 vk10 | Telecom Management; Charging for 5G Data Connectivity | Rel-20 |
| TS 32.256 vj40 | 5G Connection & Mobility Charging Spec | Rel-19 |
| TS 32.808 v1800 | Common User Profile Storage Framework | Rel-8 |
| TS 32.843 vd00 | PS Domain Online Charging in Roaming | Rel-13 |
| TR 32.901 vj00 | UDC Application Data Models Study | Rel-19 |
| TS 33.127 vj50 | Lawful Interception Architecture and Functions | Rel-19 |
| TS 33.501 vk00 | 5G Security Architecture and Procedures | Rel-20 |
| TS 33.514 vk00 | 5G Security Assurance for UDM | Rel-20 |
| TS 33.530 vj00 | Security Assurance for Unified Data Repository | Rel-19 |