1. 创建3个新的日志组

SQL> ALTER DATABASE ADD LOGFILE GROUP 4 ('/u01/app/oracle/oradata/orcl/redo06.log') SIZE 500M;

SQL> ALTER DATABASE ADD LOGFILE GROUP 5 ('/u01/app/oracle/oradata/orcl/redo05.log') SIZE 500M;

SQL> ALTER DATABASE ADD LOGFILE GROUP 6 ('/u01/app/oracle/oradata/orcl/redo06.log') SIZE 500M;

查看日志组

SQL> select * from v$logfile;

2.切换当前日志到新的日志组

SQL> alter system switch logfile;

SQL> alter system switch logfile;

SQL> alter system switch logfile;

切到要删除为INCACTIVE才行

SQL> select group#,sequence#,bytes,members,status from v$log;

GROUP#  SEQUENCE#    BYTES    MEMBERS STATUS
---------- ---------- ---------- ---------- ----------------
  1   139 52428800   1 INACTIVE
  2   137 52428800   1 INACTIVE
  3   138 52428800   1 INACTIVE
  4   140  524288000   1 ACTIVE
  5   141  524288000   1 CURRENT
  6   136  524288000   1 INACTIVE

3.删除旧的日志组

SQL> alter database drop logfile group 1;

Database altered.

SQL> alter database drop logfile group 2;

Database altered.

SQL> alter database drop logfile group 3;

查看是否删除了日志组

SQL> select group#,sequence#,bytes,members,status from v$log;

GROUP#  SEQUENCE#    BYTES    MEMBERS STATUS
---------- ---------- ---------- ---------- ----------------
  4   140  524288000   1 INACTIVE
  5   141  524288000   1 CURRENT
  6   136  524288000   1 INACTIVE

4.操作系统删除原日志组1、2、3中的文件

[oracle@oracle122 log]$ cd /u01/app/oracle/oradata/orcl
[oracle@oracle122 orcl]$ 
[oracle@oracle122 orcl]$ pwd
/u01/app/oracle/oradata/orcl
[oracle@oracle122 orcl]$ ls
control01.ctl  example01.dbf  redo01.log  redo02.log  redo03.log  redo04.log  redo05.log  redo06.log  sysaux01.dbf  system01.dbf  temp01.dbf  undotbs01.dbf  users01.dbf
[oracle@oracle122 orcl]$ rm -rf redo01.log 
[oracle@oracle122 orcl]$ rm -rf redo02.log 
[oracle@oracle122 orcl]$ rm -rf redo03.log

5.重建日志组1、2、3

SQL> ALTER DATABASE ADD LOGFILE GROUP 1 ('/u01/app/oracle/oradata/orcl/redo01.log') SIZE 500M;

SQL> ALTER DATABASE ADD LOGFILE GROUP 2 ('/u01/app/oracle/oradata/orcl/redo02.log') SIZE 500M;

SQL> ALTER DATABASE ADD LOGFILE GROUP 3 ('/u01/app/oracle/oradata/orcl/redo03.log') SIZE 500M;

7.删除中间过渡用的日志组4、5、6 ，在删除时查询select group#,sequence#,bytes,members,status from v$log; 删除组是否为INACTIVE，如果不是INACTIVE 就要执行alter system switch logfile;

查询看一下

SQL> select group#,sequence#,bytes,members,status from v$log;

GROUP#  SEQUENCE#    BYTES    MEMBERS STATUS
---------- ---------- ---------- ---------- ----------------
  1   148  524288000   1 CURRENT
  2   143  524288000   1 INACTIVE
  3   144  524288000   1 INACTIVE
  4   146  524288000   1 INACTIVE
  5   147  524288000   1 INACTIVE
  6   145  524288000   1 INACTIVE

SQL> alter database drop logfile group 4;

Database altered.

SQL> alter database drop logfile group 5;

Database altered.

SQL> alter database drop logfile group 6;

Database altered.

8.到操作系统删除组4、5、6

[oracle@oracle122 orcl]$ rm -rf redo04.log 
[oracle@oracle122 orcl]$ rm -rf redo05.log 
[oracle@oracle122 orcl]$ rm -rf redo06.log

9.备份当前最新的控制文件

SQL>  alter database backup controlfile to trace resetlogs  ;