--新建臨時日志文件

alter database add logfile group 4 (‘/u01/app/oracle/oradata/orcl/redo04.log‘) size 10m;

alter database add logfile group 5 (‘/u01/app/oracle/oradata/orcl/redo05.log‘) size 10m;

alter database add logfile group 6 (‘/u01/app/oracle/oradata/orcl/redo06.log‘) size 100m;

--切換日志文件

alter system switch logfile;

alter system switch logfile;

--刪除舊文件

alter database drop logfile group 1;

alter database drop logfile group 2;

alter database drop logfile group 3;

--操作系統刪掉1,2,3

--新建3個

alter database add logfile group 1 (‘/u01/app/oracle/oradata/orcl/redo01.log‘) size 200m;

alter database add logfile group 2 (‘/u01/app/oracle/oradata/orcl/redo02.log‘) size 200m;

alter database add logfile group 3 (‘/u01/app/oracle/oradata/orcl/redo03.log‘) size 200m;

--切換日志文件

alter system switch logfile;

alter system switch logfile;

--刪舊日志組

alter database drop logfile group 4;

--操作系統刪掉4，5

--備份控制文件

SQL> connect / as sysdba

SQL> alter database backup controlfile to trace resetlogs

原文：http://www.cnblogs.com/wolil/p/6657250.html