DataGuard - Maximum Availability mode vs sync detection

Is it possible to know if standby is synchronized with primary when DG is configured in Maximum Availability mode?

As I understand - it is not possible.
If primary dies for sure(absolutely no access to any primary files) then there is no way of knowing if it was operating in Maximum Availability(meaning standby is in sync) or downgraded into Maximum Performance mode(meaning standby is not in sync.)

What are possible solutions to this problem?

I see just one: some data of the primary db must survive the primary crash.
For example, the fact that primary went into downgraded Maximum Performance mode is recorded into background alert log. If we have access to this log then we can find in what mode the primary database operated just before the death. Alternatively, control file is the most credible source.

The question is: what is the best way to preserve this critical primary db data so that it is readily available for the third party which decides the failover? I can think of some shared storage for both control files and background logs.

Fyrirvari/Disclaimer
http://www.landsbanki.is/disclaimer

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