The HLR is a network database used for permanent management of mobile subscribers within a PLMN. It is accessible from the 3G-SGSN and the MSC. The HLR has been enhanced to include UMTS subscription data and routing information.
The VLR contains all subscriber data required for call handling and other purposes for the mobile subscribers currently located in the area controlled by the VLR. The VLR supports a mobile paging and tracking subsystem in the local area where the mobile is presently roaming.
VLR is integral part of MSC and gets updated first when a MS updates its location. Initially and timely it takes update from HLR for authenticity and facilities of the subscriber.
HLR is not integral part of MSC, and takes updates from VLR. HLR is the LR where subscibers are created and also facilities are given.