A tmnxMobGwSysGrpRedStateChange notification is generated when the the redundancy state of a group changes. [CAUSE] A working card failure, changing the redundancy configuration, or adding a protection card will trigger a change to the group's redundancy state. [EFFECT] When the value of tmnxMobGwSysGroupRedState changes from 'hot' to 'cold', a switchover has happened. No services are affected when the value of tmnxMobGwSysGroupRedState changes. [RECOVERY] After a switchover has happened, no backup card will be up. The operator needs to bring a backup card online to avoid any disruption to services in case of further failures.
Sources for this description
Nokia networking MIB copies (LibreNMS/Observium Community)