oracle在线增加redo日志组成员

文档课题：oracle在线增加redo日志组成员.
数据库：oracle 11.2.0.4
1、相关知识
oracle通过redo保证数据库事务可以被重演，从而使得在发生故障之后，数据可以被恢复.redo对于oracle数据库至关重要.为保证redo log的冗余性，一个日志组至少需配置两个成员，且最好放在不同的物理盘.在oracle日志条目过来时，会分别同时向两个成员文件写入.若其中一个发生损坏，此时还有另外一个相同的文件.
2、实际操作
SYS@orcl> select group#,bytes/1024/1024 "size(M)",status,archived from v$log;

    GROUP#    size(M) STATUS           ARC
---------- ---------- ---------------- ---
         1         50 INACTIVE         YES
         2         50 INACTIVE         YES
         3         50 CURRENT          NO

SYS@orcl> select member from v$logfile;

MEMBER
--------------------------------------------------------------------------------
/u01/app/oracle/oradata/orcl/redo03.log
/u01/app/oracle/oradata/orcl/redo02.log
/u01/app/oracle/oradata/orcl/redo01.log

SYS@orcl> alter database add logfile member '/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/redo01b.log' to group 1;

Database altered.
SYS@orcl> select group#,members,bytes/1024/1024 "size(M)",status,archived from v$log;

    GROUP#    MEMBERS    size(M) STATUS           ARC
---------- ---------- ---------- ---------------- ---
         1          2         50 INACTIVE         YES
         2          1         50 INACTIVE         YES
         3          1         50 CURRENT          NO

SYS@orcl> alter database add logfile member '/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/redo02b.log' to group 2;

Database altered.

SYS@orcl> select group#,members,bytes/1024/1024 "size(M)",status,archived from v$log;

    GROUP#    MEMBERS    size(M) STATUS           ARC
---------- ---------- ---------- ---------------- ---
         1          2         50 INACTIVE         YES
         2          2         50 INACTIVE         YES
         3          1         50 CURRENT          NO

SYS@orcl> alter system switch logfile
  2  ;

System altered.

SYS@orcl> alter system checkpoint;

System altered.

SYS@orcl> select group#,members,bytes/1024/1024 "size(M)",status,archived from v$log;

    GROUP#    MEMBERS    size(M) STATUS           ARC
---------- ---------- ---------- ---------------- ---
         1          2         50 CURRENT          NO
         2          2         50 INACTIVE         YES
         3          1         50 INACTIVE         YES

SYS@orcl> alter database add logfile member '/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/redo03b.log' to group 3;

Database altered.

SYS@orcl> select group#,members,bytes/1024/1024 "size(M)",status,archived from v$log;

    GROUP#    MEMBERS    size(M) STATUS           ARC
---------- ---------- ---------- ---------------- ---
         1          2         50 CURRENT          NO
         2          2         50 INACTIVE         YES
         3          2         50 INACTIVE         YES

SYS@orcl> select member from v$logfile;

MEMBER
--------------------------------------------------------------------------------
/u01/app/oracle/oradata/orcl/redo03.log
/u01/app/oracle/oradata/orcl/redo02.log
/u01/app/oracle/oradata/orcl/redo01.log
/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/redo01b.log
/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/redo02b.log
/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/redo03b.log

6 rows selected.

说明：如上所示，成功添加日志组成员.