Question: Upon restarting after a failure, what action does an HLR/HSS perform on subscriber data records affected by the fault, in addition to reloading data from non-volatile backup?
Option 1: It only resets all 'MS Purged' flags.
Option 2: It marks each subscriber record 'SS Check Required' (if the 'Forward Check SS Indication' service is implemented) and sends 'Reset' messages to relevant VLRs, SGSNs, MMEs, ProSe Functions, and V2X Control Functions.
Option 3: It immediately updates all location information for MSs/UEs without notifying other network elements.
Option 4: It deletes all subscriber data records to prevent potential corruption.
Explanation: Upon restarting after a failure, an HLR/HSS not only reloads data from backup but also takes additional steps to ensure data integrity and consistency across the network. This includes marking subscriber records for SS checks (if applicable) and notifying relevant VLRs, SGSNs, MMEs, ProSe Functions, and V2X Control Functions with 'Reset' messages to update their location information status regarding the HLR/HSS's knowledge of MS/UE locations. This ensures a synchronized view of subscriber data across the network after an HLR/HSS restart.