Oracle的数据库日 志称为redo log，所有数据改变都记录redo log，可以用于修复受损的数据库。Redo日志是分组的，，默认是三组。Redo日志是轮流使用的，一个redo log满了，LGWR会切换到下一组redo log，这种操作称为log switch，做log switch的同时也会做checkpoint，相应的信息还会写入控制文件。
1.查看系统的redo log信息：
SQL> select group#,sequence#,bytes,members,status from v$log;
SQL> select member from v$logfile;
2.添加日志组
alter database add logfile group 4 (\'D:\ORACLE\PRODUCT\10.2.0\ORADATA\TEST\redo04.log\') size 50m;
3.添加日志组(指定日志已经存在)
alter database add logfile group 4 (\'D:\ORACLE\PRODUCT\10.2.0\ORADATA\TEST\redo04.log\') size 50m reuse;
4.添加日志成员
alter database add logfile member \'D:\ORACLE\PRODUCT\10.2.0\ORADATA\TEST\redo0401.log\' to group 4;
5.添加日志成员(指定日志已经存在)
alter database add logfile member \'D:\ORACLE\PRODUCT\10.2.0\ORADATA\TEST\redo0401.log\' reuse to group 4;
6.删除日志组
alter database drop logfile group 4;
7.删除日志成员
alter database drop logfile member \'D:\ORACLE\PRODUCT\10.2.0\ORADATA\TEST\redo0401.log\';
8.给日志组文件换一个位置
(1)shutdown database
(2) copy the online redo log files to the new location;
(3) start database to mount;
(4)execute the command
alter database rename file \'D:\ORACLE\PRODUCT\10.2.0\ORADATA\TEST\redo0401.log\' to \'D:\ORACLE\PRODUCT\10.2.0\ORADATA\TEST\redo0401.log\';
(5)open database
9.归档Redo log文件
启动日志归档有两个好处：
select A.tablespace_name, (1 - (A.total) / B.total) * 100 used_percent
from (select tablespace_name, sum(bytes) total
from dba_free_space
group by tablespace_name) A,
(select tablespace_name, sum(bytes) total
from dba_data_files
group by tablespace_name) B
where A.tablespace_name = B.tablespace_name;
2、查询表空间文件存放位置：
select tablespace_name, file_id, file_name,round(bytes/(1024*1024),0) total_space from dba_data_files order by tablespace_name;
3、以增加方式扩增表空间
alter tablespace SYSAUX add datafile \'E:\oracle11g\oradata\orcl\SYSAUX02.DBF\' size 500M
alter tablespace SYSTEM add datafile \'D:\ORACLE\ORADATA\XKXXOA\SYSTEM04.DBF\' size 3000M
alter tablespace "gtp-default" add datafile \'D:\ORACLE\PRODUCT\11.2.0\DBHOME_1\DATABASE\GTP-DEFAULT3.DBF\' size 1500M
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