alter database add logfile member '<filename>' to group <group>;
List members and sizes
col member format a60
col "Size MB" format 9,999,999
select lf.member
, ceil(lg.bytes / 1024 / 1024) "Size MB"
from v$logfile lf
, v$log lg
where lg.group# = lf.group#
order by 1
/
