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
In the Network Map
- Mobile Network → 5G Core → UDR (Shared Data Environment)
Evolution Lineage
- Evolved from: HSS (4G→5G)
- Network evolution overview →
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (74 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the UDR (Unified Data Repository) was formally introduced as a new facility for user data convergence, designed to store and manage user profile data in a common, centralized way using a defined data model. The release specified its core capabilities, including the storage of non-real-time data like subscriber and policy profiles, while explicitly excluding user content data. Furthermore, it detailed critical operational aspects such as UDR discovery and selection procedures, error handling, subscription mechanisms, and the definition of its API interfaces.
- Clarification on UDR TS 23.501CR0061
- Update and correction of table for AMF, UDM, UDR, NSSF, UDSF and BSF services TS 23.501CR0363
- 23.501: AUSF, UDM, UDR Discovery TS 23.501CR0594
- UDR selection TS 23.501CR0741
- Error handling in UDR TS 29.504CR0004
- UDR Subscriptions TS 29.505CR0057
+ 4 more changes
In Release 16, the UDR function was enhanced with new capabilities including support for subscription segmentation, the storage of HTTP headers, and a service for mapping IMS Public Identities to HSS Group IDs for HSS selection. It also gained functionality for NF Group ID association and integration with the NRF for group ID mapping, while procedures were corrected for subscription creation and invalid policy removal. These updates refined the UDR's role in the converged data architecture without altering its core principle of managing subscriber and service data models separately from content storage.
- eSBA communication schemas related to UDM and UDR discovery and selection TS 23.501CR0800
- Adding UDR NF Group ID association functionality TS 23.501CR1384
- 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
- HTTP Header storage in UDR TS 29.503CR0415
+ 7 more changes
In Release 17, the UDR function was enhanced with new capabilities including support for restoration notifications and procedures, the ability for new Network Functions like the SOR-AF and HSS to act as consumers, and the storage of new data types such as Time Synchronization information and non-subscriber related data. It also introduced specific features to support Traffic Steering Control (TSC) and Data Collection, Analytics, and Model Training (DCAMP), as well as mechanisms for updating application data to influence UE Route Selection Policy (URSP). Furthermore, the release defined procedures for managing subscriptions and handling policy retrieval, including the assignment of a `resetId` to consumers like the PCF and NEF.
- 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
+ 12 more changes
In Release 18, the UDR was enhanced to support new data subsets and functionalities for emerging network features. Specifically, it gained the capability to store DNAI-EAS Mappings data, manage a BDT warning notification indication and AS address, and support the new "GMEC" feature. The release also introduced a UDR control flag for NSWO, enabled the PCF to query with multiple S-NSSAIs, and completed the HR-SBO functionality while correcting 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
- Support of updating restricted status in UDR TS 29.513CR0543
- Support of updating restricted status in UDR TS 29.519CR0500
+ 7 more changes
In Release 19, the Unified Data Repository (UDR) was enhanced with several new capabilities, including support for storing an AF-specific UE identifier generated by the UDM and the detailed outcome of UE policy delivery. It also gained new functions for managing data related to Ambient IoT and for handling the Device Identifier of non-3GPP devices connecting behind a UE, alongside additions for traffic influence and UP path change event outcomes. Furthermore, the release introduced mechanisms for data restoration for "anyUE"-identified data and a UDR control flag for NSWO.
- 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 |
