Oracle Error Message
ORA-16447: Redo apply was not active at the target standby database
Reason for the Error
ALTER SYSTEM FLUSH REDO TO STANDBY failed because redo apply is not active at the target database.
Solution
Start redo apply at the standby database and reissue the ALTER SYSTEM FLUSH REDO TO STANDBY statement, or reissue the ALTER SYSTEM FLUSH REDO TO STANDBY statement with the NO CONFIRM APPLY clause.