Fault Domains and Availability

Summary

What happens if a fault domain goes down?

Content

HI

I have 4 compute instances , 2 apps tiers , 2 with standalone Oracle DB's 
The application cannot justify more than a single instance for each of the functions. i.e no RAC , no shared apps tiers, no standby, just 4 boxes each doing a separate function within the system.

I have created all 4 instances in a single fault domain in an AD ( as implied by the documentation https://docs.oracle.com/en/solutions/design-dr/determine-your-deployment-strategy1.html#GUID-C12D99C4-A027-4395-8D0F-A73179862240) .

The application can be unavailable for a period of time (length of which would depend on the point in the month)