ORA-16636: fast-start failover target standby in error state, cannot stop observer
Cause: A STOP OBSERVER operation could not be completed when fast-start failover was enabled because the target standby database could not participate in the STOP OBSERVER operation.
Action: Additional information about this failure is recorded in the Data Guard broker log file for the primary database. This information helps to identify the reason why the target standby database was unable to participate in the STOP OBSERVER operation. If the problem can be corrected by the information in the broker log file, retry the operation. Alternatively, fast-start failover may be forcibly disabled by connecting to the primary database and issuing the DISABLE FAST_START FAILOVER FORCE command from the DGMGRL CLI. Once fast-start failover has been forcibly disabled, the observer can be stopped regardless of the current state of the target standby database.