Message Oracle ORA-38748 - cannot flashback data file string - file is in use or recovery

ERRORcannot flashback data file string - file is in use or recovery
CAUSEAn attempt to do FLASHBACK DATABASE found that the file was not available for recovery. Either it was online and the database was open in some instance, or another process was currently doing media recovery or flashback on the file.
ACTIONDo not do FLASHBACK DATABASE.