How do Oracle RAC instance alarms fire and what is the agent flow?
Alarms on RAC instances status are as follows
1. OS connect availability: raised if the RAC instance host is unavailable
2. RAC instance availability: raised if the RAC instance's process/service is down
3. RAC instance connect availability: raised if it is impossible to connect to the RAC instance itself.
The agent's flow is as follows:
It first tries to connect to the instance host through OS connection. If it fails, alarm 1 is raised. If it succeeds, it then checks the instance status and raises alarm 2, if the instance is down.
Please note: RAC alarms work only, if the "OS Collection" is enabled
