ADD [ STANDBY ] LOGFILE
   { 
     { [ INSTANCE 'instance_name' ] | [ THREAD 'integer' ] }
     [ GROUP integer ] redo_log_file_spec
       [, [ GROUP integer ] redo_log_file_spec ]...
   | MEMBER 'filename' [ REUSE ] [, 'filename' [ REUSE ] ]...
        TO logfile_descriptor [, logfile_descriptor ]...
   }