sentences:  This procedure is used to update the location of the Mobile Station in the network and is described in more detail here.When a mobile station registers in a new VLR, the subscriber's data is deleted from the
  previous VLR in a cancel location procedure.The HLR initiates the procedure when it
  receives an 'update location' message from a VLR other than the one in which the MS
  was located at the time when its location information was last updated in the HLR database.