ORA-16447 Redo apply was not active at the target standby database

Cause

ALTER SYSTEM FLUSH REDO TO STANDBY failed because redo apply is not active at the target database.

Action

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.

alter database recover managed standby database disconnect from session;