SQL>alter database add logfile thread 1 group 9
('+DATA/orcl/onlinelog/group_9_redo_log.log', '+BAK/orcl/onlinelog/group_9_redo_log.log') size 50m;
Database altered.
SQL>alter database add logfile thread 2 group 10
('+DATA/orcl/onlinelog/group_10_redo_log.log', '+BAK/orcl/onlinelog/group_10_redo_log.log') size 50m;
Database altered.
请教这个+DATA 和 +BAK 是什么意思,是指哪个目录?