Plain-language definition
The database of an operator's subscribers and where they currently are.
Technical definition
The HLR stores IMSI, MSISDN, services, CAMEL subscription data and current serving MSC/VLR and SGSN; it answers SRI-SM for SMS routing and holds Message Waiting Data.
Why it matters
Every MT SMS depends on an HLR answer, and HLR data underpins home routing, MNP checks and firewall correlation.
Last reviewed 2026-09-12 by the Guardivia QoS Engineering Team. Product facts on this page describe current capabilities; items marked “where supported”, “optional”, “integration” or “consultancy” are confirmed per deployment.