修改重做日志文件(redolog)大小

SQL> select group#,sequence#,bytes/1024/1024 sizeMB,members,status from v$log;

    GROUP#  SEQUENCE#     SIZEMB    MEMBERS     STATUS
---------- ---------- ---------- ----------   ---------  
         1    27             50          1     INACTIVE
         2    28             50          1     CURRENT
         3    29             50          1     INACTIVE

inactive：表示实例恢复已不再需要这组联机重做日志组了。
active：表示该组是活动的但不是当前组，实例恢复时需要这组日志。
current：表示该组日志是当前组，该联机重做日志组是活动的，当前正在使用。
unused：表示该日志组从未写过，是重做日志刚刚添加到状态。

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

    GROUP# STATUS  TYPE    MEMBER
---------- ------- ------- ---------------------------------------------
         3  ONLINE  /home/app/oracle/oradata/orcl/redo03.log
         2  ONLINE  /home/app/oracle/oradata/orcl/redo02.log
         1  ONLINE  /home/app/oracle/oradata/orcl/redo01.log

空白：表示该文件正在使用。
stale：表示该文件中的内容是不完全的。
invalid：表示该文件是不可以被访问的。
deleted：表示该文件已不再有用了。

SQL> alter database add logfile group 4(\‘/home/app/oracle/oradata/orcl/redo04.log\‘) size 50M;

Database altered.

SQL> alter database add logfile group 5(\‘/home/app/oracle/oradata/orcl/redo05.log\‘) size 500M;

Database altered.

SQL> alter system checkpoint;

System altered.

SQL> alter system switch logfile;

System altered.

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> alter database add logfile group 1(\‘//home/app/oracle/oradata/orcl/redo01.log\‘) size 1024M;

Database altered.

SQL> alter database add logfile group 2(\‘//home/app/oracle/oradata/orcl/redo02.log\‘) size 1024M;

Database altered.

SQL> alter database add logfile group 3(\‘/home/app/oracle/oradata/orcl/redo03.log\‘) size 1024M;

Database altered.

SQL> alter system checkpoint;

System altered.

SQL> alter system switch logfile;

System altered.

SQL> alter database drop logfile group 4;

Database altered.

SQL> alter database drop logfile group 5;

Database altered.