Home loction registers (HLR):

• Permanent database about mobile subscribers in a large service area (generally one per GSM network operator)
• Database contains subscriber and location information
  • Database contains IMSI (international mobile subscriber identity), prepaid/postpaid, roaming restrictions, supplementary services
• Each subscriber assigned IMSI to identify home user

Visitor LOcation REgisters (VLR):

• Temporary databse which slres IMSI and custormer information for each roaming subscriber visitying the coverage area of particular MSC
• It updates whenever new MS enters its area, by HLR database.
• It controls the mobiles roaming in its area