ORA-16529
Switchover and failover operations are restricted to databases specified in the PrimaryDatabaseCandidates configuration property.
Cause
An attempt is being made to switchover or failover to a database that is not specified in the PrimaryDatabaseCandidates configuration property.
Action
Check the value of the PrimaryDatabaseCandidates configuration property and specify a database for switchover or failover that is listed. Alternatively, add the database that was specified in the switchover or failover command to the PrimaryDatabaseCandidates configuration property or reset the property value.