在线修改online redo logfiles size 大小

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在线修改online redo logfiles size 大小

oracle redolog size 过小有时候会导致性能问题，现在我们在线修改redolog，一般在业务量比较小的时候进行此操作

1. 首先查看当前的日志组大小，路径名

[oracle@tora10 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.4.0 - Production on Sat Feb 23 17:08:33 2013

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

    GROUP#      BYTES STATUS
---------- ---------- ----------------
         1 524288000 INACTIVE
         2 524288000 CURRENT
         3 524288000 INACTIVE

    当前的日志组大小是 512MB 文件系统，每个组成员只有1个member

   SQL> select group#, member from v$logfile;

    GROUP# MEMBER
---------- ----------------------------------------
         1 /opt/oracle/oradata/test/redo01.log
         2 /opt/oracle/oradata/test/redo02.log
         3 /opt/oracle/oradata/test/redo03.log


2. 现在创建新的redolog group 4, 5, and 6 每个log大小为1024MB

   SQL> alter database add logfile group 4
           '/opt/oracle/oradata/test/redo04.log ' size 1024M;

   SQL> alter database add logfile group 5
           '/opt/oracle/oradata/test/redo05.log ' size 1024M;

   SQL> alter database add logfile group 6
           '/opt/oracle/oradata/test/redo06.log ' size 1024M;


3. 创建完新的日志组后，查询所有日志组状态:

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

      GROUP# STATUS
   --------- ----------------
           1 INACTIVE
           2 CURRENT
           3 INACTIVE
           4 UNUSED
           5 UNUSED
           6 UNUSED

   当前使用的是group 2 日志组，现在通过“多次”切日志换命令将group 1,2,3状态变为INACTIVE，
让oracle使用新建的group4,5,6，然后将小的日志组group 1,2,3删除


   SQL> alter system switch logfile;

   SQL> alter system checkpoint;

4.切换完成后，再次查询当前的日志组状态，当前使用的日志组是group 5

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


      GROUP# STATUS
     -------- ------
         1 INACTIVE
         2 INACTIVE
         3 INACTIVE
         4 INACTIVE
         5 CURRENT
         6 INACTIVE
    当redolog group 1,2,3状态为active时，意味着不能删除当前redo,直至用"alter system switch log file" ，"alter system checkpoint"
命令将其切换为“inactive”状态才能将其删除


5.删除group 1,2,3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;
        Database altered.


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

      GROUP#     BYTES STATUS
   --------- --------- ----------------
           4 10485760 CURRENT
           5 10485760 UNUSED
           6 10485760 UNUSED

6. 整个操作完成后，最好做一个backup

7.在操作系统层面删除原来的redolog

[oracle@tora10 ~]$ cd /opt/oracle/oradata/test/
[oracle@tora10 test]$ ll -al redo*
-rw-r----- 1 oracle oinstall 524288512 Feb 23 17:15 redo01.log
-rw-r----- 1 oracle oinstall 524288512 Feb 23 17:15 redo02.log
-rw-r----- 1 oracle oinstall 524288512 Feb 23 17:15 redo03.log
-rw-r----- 1 oracle oinstall 1073742336 Feb 23 17:16 redo04.log
-rw-r----- 1 oracle oinstall 1073742336 Feb 23 17:16 redo05.log
-rw-r----- 1 oracle oinstall 1073742336 Feb 23 17:17 redo06.log

删除小的redolog

[oracle@tora10 test]$ rm -rf redo01.log
[oracle@tora10 test]$ rm -rf redo02.log
[oracle@tora10 test]$ rm -rf redo03.log


值得注意的是，加完新的redolog group 后，要监控下alert log 查看新的redolog的切换频率与原来情况相比较

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