Debugging Node Eviction Issues
One of the most common and complex issues in Oracle RAC is performing the root cause analysis (RCA) of the node eviction issues. Oracle evicts a node from the cluster mainly due to one of the following three reasons:
The node is not able to complete the network heartbeat (NHB).
The node is not able to complete the disk heartbeat (DHB).
The node does not have enough CPU to perform either of the heartbeat operations. ...