Oracle : Ошибка ORA-16820

16820, 0000, "fast-start failover observer is no longer observing this database"
*Cause: A previously started observer was no longer actively observing this
database. A significant amount of time elapsed since this
database last heard from the observer.
Possible reasons were:
- The host where the observer was running was not available.
- The network connection between the observer and this database
was not available.
- The observer process was terminated unexpectedly.
*Action: Check the reason why the observer cannot contact this database.
If the problem cannot be corrected, stop the current observer by
connecting to the Data Guard configuration and issue the DGMGRL
STOP OBSERVER command. Then, restart the observer on another
host. Finally, use the DGMGRL START OBSERVER command to start the
observer on the other host.

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