HLR
Home Location Register
The Home Location Register is a database within the HPLMN (Home Public Land Mobile Network). It provides routing information for MT (Mobile Terminated) calls and SMS (Short Message Service). It is also responsible for the maintenance of user subscription information. This is distributed to the relevant VLR (Visitor Location Register) or SGSN (Serving GPRS Support Node) through the attach process and mobility management procedures such as Location Area and Routing Area updates.