16636, 0000, "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.