Oracle RAC环境下redo log 文件的扩容

环境：

• 有一个2节点RAC
• 每一个节点2个logfile group
• 每一个group含2个member
• 每一个member的大小为200M

目标：将每一个member的大小有200M扩充到1G。

先来看下redo log的配置：

SQL> select * from v$log;GROUP#    THREAD#    SEQUENCE#        BYTES    BLOCKSIZE    MEMBERS    ARCHIVED      STATUS    FIRST_CHANGE#    FIRST_TIME           NEXT_CHANGE#    NEXT_TIME    CON_ID
_________ __________ ____________ ____________ ____________ __________ ___________ ___________ ________________ _____________ ______________________ ____________ _________1          1          337    209715200          512          2 NO          INACTIVE             2820063 14-DEC-23                    2838640 14-DEC-23            02          1          338    209715200          512          2 NO          CURRENT              2838640 14-DEC-23        9295429630892703743                      03          2            1    209715200          512          2 NO          INACTIVE             2195630 13-DEC-23                    2713793 14-DEC-23            04          2            2    209715200          512          2 NO          CURRENT              2713793 14-DEC-23        9295429630892703743                      0SQL> select * from v$logfile order by group#;GROUP#    STATUS      TYPE                                           MEMBER    IS_RECOVERY_DEST_FILE    CON_ID
_________ _________ _________ ________________________________________________ ________________________ _________1           ONLINE    +RECOC1/ORCL/ONLINELOG/group_1.624.1155482177    YES                              01           ONLINE    +DATAC1/ORCL/ONLINELOG/group_1.693.1155482175    NO                               02           ONLINE    +RECOC1/ORCL/ONLINELOG/group_2.625.1155482177    YES                              02           ONLINE    +DATAC1/ORCL/ONLINELOG/group_2.694.1155482175    NO                               03           ONLINE    +DATAC1/ORCL/ONLINELOG/group_3.697.1155482693    NO                               03           ONLINE    +RECOC1/ORCL/ONLINELOG/group_3.626.1155482693    YES                              04           ONLINE    +DATAC1/ORCL/ONLINELOG/group_4.698.1155482693    NO                               04           ONLINE    +RECOC1/ORCL/ONLINELOG/group_4.627.1155482693    YES                              08 rows selected.

有几个实例，就有几个thread：

SQL> select thread#,status from v$thread;THREAD#    STATUS
__________ _________1 OPEN2 OPEN

从SQL Developer中看到的配置：

直接删掉group重建是不行的，因为每一个实例必须保证最少2个group。

SQL> ALTER DATABASE DROP LOGFILE GROUP 1;Error starting at line : 1 in command -
ALTER DATABASE DROP LOGFILE GROUP 1
Error report -
ORA-01567: dropping log 1 would leave less than 2 log files for instance orcl1 (thread 1)
ORA-00312: online log 1 thread 1: '+DATAC1/ORCL/ONLINELOG/group_1.693.1155482175'
ORA-00312: online log 1 thread 1: '+RECOC1/ORCL/ONLINELOG/group_1.624.1155482177'
01567. 00000 -  "dropping log %s would leave less than 2 log files for instance %s (thread %s)"
*Cause:    Dropping all the logs specified would leave fewer than the requiredtwo log files per enabled thread.
*Action:   Either drop fewer logs or disable the thread before deleting thelogs. It may be possible to clear the log rather than drop it.

方法其实简单，就是先加一个临时的redo log file group，然后就可以删除重建了，最终再把这个临时的删除就好。

先处理2个状态为Inactive的log file group，即#1和#3，因为他们可以直接删。

先对实例1上的#1进行操作：

ALTER DATABASE ADD LOGFILE THREAD 1 GROUP 5 ('+DATAC1') SIZE 200M;
ALTER DATABASE DROP LOGFILE GROUP 1;
ALTER DATABASE ADD LOGFILE THREAD 1 GROUP 1 ('+DATAC1', '+RECOC1') SIZE 1G;
ALTER DATABASE DROP LOGFILE GROUP 5;

再对实例2上的#3进行操作：

ALTER DATABASE ADD LOGFILE THREAD 2 GROUP 5 ('+DATAC1') SIZE 200M;
ALTER DATABASE DROP LOGFILE GROUP 3;
ALTER DATABASE ADD LOGFILE THREAD 2 GROUP 3 ('+DATAC1', '+RECOC1') SIZE 1G;
ALTER DATABASE DROP LOGFILE GROUP 5;

现在logfile group 1和3都改好了，还剩#2和#4。

先对实例1上的#2进行操作：

ALTER DATABASE ADD LOGFILE THREAD 1 GROUP 5 ('+DATAC1') SIZE 200M;

此时无法删除#2，因为他的状态是current：

SQL> ALTER DATABASE DROP LOGFILE GROUP 2;
ALTER DATABASE DROP LOGFILE GROUP 2
*
ERROR at line 1:
ORA-01623: log 2 is current log for instance orcl1 (thread 1) - cannot drop
ORA-00312: online log 2 thread 1:
'+DATAC1/ORCL/ONLINELOG/group_2.694.1155482175'
ORA-00312: online log 2 thread 1:
'+RECOC1/ORCL/ONLINELOG/group_2.625.1155482177'

先做一次log switch：

SQL> alter system switch logfile;System altered.

此时#2的状态变为Active，但仍无法删除，因为其要用于实例恢复：

SQL> ALTER DATABASE DROP LOGFILE GROUP 2;
ALTER DATABASE DROP LOGFILE GROUP 2
*
ERROR at line 1:
ORA-01624: log 2 needed for crash recovery of instance orcl1 (thread 1)
ORA-00312: online log 2 thread 1:
'+DATAC1/ORCL/ONLINELOG/group_2.694.1155482175'
ORA-00312: online log 2 thread 1:
'+RECOC1/ORCL/ONLINELOG/group_2.625.1155482177'

过一会，其状态变为Inactive，就可以删除了。如果实在等不急，也可以运行命令ALTER SYSTEM CHECKPOINT：

ALTER DATABASE DROP LOGFILE GROUP 2;
ALTER DATABASE ADD LOGFILE THREAD 1 GROUP 2 ('+DATAC1', '+RECOC1') SIZE 1G;
ALTER DATABASE DROP LOGFILE GROUP 5;

实例2也可以照此操作（连接到实例2运行）：

ALTER DATABASE ADD LOGFILE THREAD 2 GROUP 5 ('+DATAC1') SIZE 200M;
alter system switch logfile;
ALTER SYSTEM CHECKPOINT;
ALTER DATABASE DROP LOGFILE GROUP 4;
ALTER DATABASE ADD LOGFILE THREAD 2 GROUP 4 ('+DATAC1', '+RECOC1') SIZE 1G;
ALTER DATABASE DROP LOGFILE GROUP 5;

好了，修改成功。