在联机状态改变redo logfile大小的方法 

    假如原来有3个小的redo log file, 下面是UNIX环境下的一个例子:

     第一步: 往数据库添加三个大的redo logfile

    SVRMGRL>ALTER DATABASE ADD LOGFILE GROUP 4

        ('/opt/oradata/app/redo04.log','/ora_bak/oradata2/redolog/redo04.log') size 16M reuse; 

     SVRMGRL>ALTER DATABASE ADD LOGFILE GROUP 5

         ('/opt/oradata/app/redo05.log','/ora_bak/oradata2/redolog/redo05.log') size 16M reuse; 

     SVRMGRL>ALTER DATABASE ADD LOGFILE GROUP 6

         ('/opt/oradata/app/redo06.log', '/ora_bak/oradata2/redolog/redo06.log') size 16M reuse;          

    第二步: 手工地做log switch, 使新建的redo logfile起作用.

        SVRMGRL>alter system switch logfile;

    此操作可以执行一到几次, 使旧的redo logfile成inactive状态.

    第三步: 删除原来旧的redo logfile.

        SVRMGRL>alter database drop logfile group 1; 

    SVRMGRL>alter database drop logfile group 2; 

    SVRMGRL>alter database drop logfile group 3;  

本文出自 “superping” 博客，谢绝转载！