This topic describes how protection modes behave during primary/standby role changes.
Failover
If the primary fails while in maximum protection or at maximum availability level, a standby can become primary through failover with no data loss.
During failover, whatever protection mode and level the standby had before, the system switches it directly to maximum performance.
Switchover
After switchover turns the former primary into a standby, you can promote either a strongly synchronized standby or a non-strongly-synchronized standby to be the new primary:
Promote a strongly synchronized standby: If that standby had configured a strongly synchronized downstream before the switch, and both sides point their upstream at each other (the old standby's upstream is the old primary, and the old primary's upstream is the old standby), its protection mode can stay maximum protection. If it had not set such a downstream, when it becomes primary the system sets its protection mode to maximum performance.
Promote a non-strongly-synchronized standby: Such standbys are always at maximum performance. After promotion they remain maximum performance, but log streams are still in a strong-sync state, so you must complete write quiesce and downgrade successfully before normal writes resume.
The following scenarios illustrate this:
In a network-based physical standby setup, suppose tenant A is primary in maximum protection, B is its strongly synchronized standby, and C is an asynchronous standby whose upstream is A.
If switchover demotes A to standby, you can promote B or C to primary.
Scenario 1:
Promote B to primary, and before that set B's strongly synchronized downstream to A. After the switch, B's protection mode stays maximum protection.
Scenario 2:
Promote B without configuring a strongly synchronized downstream for B. After the switch, B falls back to maximum performance; A's protection mode also becomes maximum performance once it ingests new upstream data.
Scenario 3:
Promote C. Its protection mode falls back to maximum performance; A and B likewise move to maximum performance after they receive new upstream data.