...
The PROM instance in each SDN-C site is responsible for periodically ascertaining the health of the local site based on the health of each component (see SDN-C Site Health Determination). This information is published to MUSIC in order for the remote site to also be aware of this information.
If the local PROM instance determines that the site is currently 'standby' and the remote site has become unhealthy, it will proceed to automatically initiate failover procedures, making the local site 'active' while the remote site is reverted to 'standby' (provided it is in good enough state to do so).
The following script can be used to switch between the primary and secondary roles for an SDNC server.
...