Set up a mirroring system to ensure the availability of your tenant database.
You must have:
Two cloud servers to run the mirror and the arbiter. The major and minor version of these cloud servers must be the same as the cloud server that runs the primary database.
The AddDatabase and AlterTenantMirroring privileges.
The database cannot be an autostart database.
A mirroring system involves two cloud servers running the primary and mirror databases, and one cloud server running as arbiter, which negotiates which database is the read-write copy.
Connections to the database are temporarily disabled during the process of enabling tenant mirroring.
Your tenant mirroring system now contains a primary, a mirror, and an arbiter.
(Optional) Add read-only scale-out to your tenant mirroring system by creating scale-out database copies.