If the agent running on the Master database node detects a failure of the Master database, Failover Manager begins the process of confirming the failure (see Figure 8.1).If the agent on the Master node detects that the Master database has failed, all agents attempt to connect directly to the Master database. If an agent can connect to the database, Failover Manager sends a notification about the state of the Master node. If no agent can connect, the Master agent declares database failure and releases the VIP (if applicable).If no agent can reach the virtual IP address or the database server, Failover Manager starts the failover process. The Standby agent on the most up-to-date node runs a fencing script (if applicable), promotes the Standby database to Master database, and assigns the virtual IP address to the Standby node. Any additional Standby nodes are configured to replicate from the new master unless auto.reconfigure is set to false. If applicable, the agent runs a post-promotion script.
2. Invoke the efm resume command on the original Master node.After returning the node to the cluster as a Standby, you can easily return the node to the role of Master:
1. If the cluster has more than one Standby node, use the efm allow-node command to set the node's failover priority to 1.