GSM 09.02 - Version 5.3.0 - Digital cellular telecommunications - ETSI

Page 366
GSM 09.02 Version 5.3.0: August 1996
16.3.2 HLR fault recovery procedures
The following processes are involved with the restart of the HLR:
- HLR_RESTART subclause 16.3.2;
- REC_RESET_IN_VLR subclause 16.3.2.
In the case of a location registration request from the MS, the following processes are involved with the
HLR restoration procedure:
- Update_Location_Area_VLR subclause 16.1.1.3;
- Update_Location_HLR subclause 16.1.1.4.
In the case of a mobile originated service request, the
- Macro Process_Access_Request_VLR subclause 21.4.2; and the
- Process Update_Location_HLR subclause 16.1.1.4,
are involved with the HLR restoration procedure.
For the HLR, periodic back-up of data to non-volatile memory is mandatory.
Data that have been changed in the period of time after the last back-up storage and before the restart of
the HLR cannot be recovered by reload from the non-volatile memory. Therefore, a restoration procedure
is triggered individually for each IMSI record that has been affected by the HLR fault at the first
authenticated radio contact that is established with the MS concerned.
The HLR restoration procedure forces updating of MSC number, VLR number and, if provided by the VLR,
LMSI in the HLR. Consistency of subscriber data that are stored in the VLR for an MS that has been
affected by a HLR fault with the subscriber data stored in the HLR for this MS will be achieved.
As an implementation option, a notification can be forwarded to the MS to alert the subscriber to check the
parameters for supplementary services that allow subscriber controlled input
(MAP_FORWARD_CHECK_SS_INDICATION service). If the VLR receives this notification from the HLR it
shall forward the notification to the MS.
Figure 16.3/2 illustrates the signalling sequence for HLR restoration.
After a restart, the home location register performs the following actions for the subscriber data records
that have been affected by the HLR fault (see figure 16.3/3):
- reload all data from the non-volatile back-up;
- if the MAP_FORWARD_CHECK_SS_INDICATION service is implemented, mark each subscriber
record "SS Check Required" by setting the "Check SS" indicator;
- set subscriber tracing deactive in the VLR for each of its Mss;
- reset the "MS Purged" flag for each of its MSs;
- send a MAP_RESET request to the VLRs where its MSs are located (see figure 16.3/4).
The MAP_RESET request contains the HLR number and optionally the HLR Identity List.
When receiving a MAP_RESET indication, the VLR will derive all involved MSs of that HLR either from the
HLR Identity List (if present), or from the HLR number. The VLR will then mark these MSs with the
indicator "Location Information Confirmed in HLR" set to "Not Confirmed" and will deactivate all subscriber
tracings for these Mss (see figure 16.3/5).