Cause
The standby server in a duplex system is nonoperational for longer than 15 minutes and cannot generate alarm on its own behalf. Typical causes are:
The rolling Linux reboots due to reloading of a rolling Communication Manager or a failure to start Communication Manager.
A server was turned down (manually or UPS failure) for more than 15 minutes without first being taken out of service (busied out). The correct procedure for doing a stop on a standby server is to busy it out first, then stop it.