Oracle 9i DBA Fundamentals I 学习笔记（七）

Chapter 07— maintaining online redo log files
1、联机重做日志文件
•记录对数据库数据所做的所有改变（写入的信息包括尚未提交的事务处理、还原段信息以及方案和对象管理语句）
•提供一种恢复的机制
•被组织成组
•至少有两组（同一个组内的联机重做日志成员是相同的）

2、下面的参数限制了联机重做日志文件的数量：
• CREATE DATABASE 命令中的MAXLOGFILES 参数指定联机重做日志文件组的绝对最大数量（MAXLOGFILES 的最大值和缺省值取决于操作系统）
• CREATE DATABASE 命令所使用的MAXLOGMEMBERS 参数决定每个组的成员的最大数量（MAXLOGMEMBERS 的最大值和缺省值取决于操作系统）

3、检查点可发生在下面情况中：
• 每次日志切换时
• 当已通过正常、事务处理或者立即选项关闭例程时
• 通过设置初始化参数FAST_START_MTTR_TARGET 强制执行时
• 数据库管理员通过手动方式请求时
• ALTER TABLESPACE [OFFLINE NORMAL|READ ONLY|BEGIN BACKUP] 命令导致对特定数据文件执行检查点操作时
如果初始化参数LOG_CHECKPOINTS_TO_ALERT 设置为TRUE，则有关每个检查点的信息都记录在alert_SID.log 文件内。该参数缺省值为FALSE，表示不记录检查点。

4、强制日志切换：
SQL> desc v$log;
Name Null? Type
----------------------------------------- -------- ----------------------------
GROUP# NUMBER
THREAD# NUMBER
SEQUENCE# NUMBER
BYTES NUMBER
MEMBERS NUMBER
ARCHIVED VARCHAR2(3)
STATUS VARCHAR2(16)
FIRST_CHANGE# NUMBER
FIRST_TIME DATE

SQL>

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

GROUP# THREAD# SEQUENCE# STATUS
---------- ---------- ---------- ----------------
1 1 2 INACTIVE
2 1 3 INACTIVE
3 1 4 CURRENT

SQL>

SQL> alter system switch logfile;

System altered.

SQL>

切换后：
SQL> select group#,thread#,sequence#, status from v$log;

GROUP# THREAD# SEQUENCE# STATUS
---------- ---------- ---------- ----------------
1 1 5 CURRENT
2 1 3 INACTIVE
3 1 4 ACTIVE

SQL>

强制检查点发生：
SQL> alter system checkpoint;

System altered.

SQL>

5、增加联机重做日志组：
先查看组的情况：
SQL> desc v$logfile;
Name Null? Type
----------------------------------------- -------- ----------------------------
GROUP# NUMBER
STATUS VARCHAR2(7)
TYPE VARCHAR2(7)
MEMBER VARCHAR2(513)

SQL>

SQL> select * from v$logfile;

GROUP# STATUS TYPE MEMBER
---------- ------- ------- ------------------------------
3 ONLINE /u01/oradata/denver/redo03.log
2 STALE ONLINE /u01/oradata/denver/redo02.log
1 ONLINE /u01/oradata/denver/redo01.log

SQL>

创建：
SQL> alter database add logfile group 4
2 ('/u01/oradata/denver/redo04.log') size 50M;

Database altered.

SQL>

创建后：
SQL> select * from v$logfile;

GROUP# STATUS TYPE MEMBER
---------- ------- ------- ------------------------------
3 ONLINE /u01/oradata/denver/redo03.log
2 STALE ONLINE /u01/oradata/denver/redo02.log
1 ONLINE /u01/oradata/denver/redo01.log
4 ONLINE /u01/oradata/denver/redo04.log

SQL>
6、增加联机重做日志组成员：

SQL> alter database add logfile member
2 '/u01/oradata/denver/redo04a.log' to group 4;

Database altered.

SQL>

增加后：
SQL> select * from v$logfile;

GROUP# STATUS TYPE MEMBER
---------- ------- ------- -----------------------------------
3 ONLINE /u01/oradata/denver/redo03.log
2 STALE ONLINE /u01/oradata/denver/redo02.log
1 ONLINE /u01/oradata/denver/redo01.log
4 ONLINE /u01/oradata/denver/redo04.log
4 INVALID ONLINE /u01/oradata/denver/redo04a.log

SQL>

7、删除日志成员：
删除前：
SQL> select * from v$logfile;

GROUP# STATUS TYPE MEMBER
---------- ------- ------- ------------------------------
3 ONLINE /u01/oradata/denver/redo03.log
2 STALE ONLINE /u01/oradata/denver/redo02.log
1 STALE ONLINE /u01/oradata/denver/redo01.log
4 ONLINE /u01/oradata/denver/redo04.log
4 ONLINE /u01/oradata/denver/redo04a.lo
g

SQL>

删除：
SQL> alter database drop logfile member '/u01/oradata/denver/redo04a.log';

Database altered.

SQL>

删除后：
SQL> select * from v$logfile;

GROUP# STATUS TYPE MEMBER
---------- ------- ------- ------------------------------
3 ONLINE /u01/oradata/denver/redo03.log
2 ONLINE /u01/oradata/denver/redo02.log
1 STALE ONLINE /u01/oradata/denver/redo01.log
4 ONLINE /u01/oradata/denver/redo04.log

SQL>

8、删除组
删除前：

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

GROUP# MEMBERS ARC STATUS
---------- ---------- --- ----------------
1 1 YES INACTIVE
2 1 NO CURRENT
3 1 YES INACTIVE
4 1 YES ACTIVE

SQL>

删除
alter database drop logfile group 4;

9、清空redo：
SQL> alter database clear logfile group 3;

10、重命名、重分配日志文件（两种方法）
（1）、添加新成员，删除旧成员
（2）、ALTER DATABASE RENAME FILE command
•shutdown the database
•copy the database redo log files to the new location
•place the database in MOUNT mode
•execute the command
Eg:
（ALTER DATABASE RENAME FILE
‘$HOME/ORACLE/u01/log2a.rdo’
TO ‘$HOME/ORACLE/u02/log1c.rdo’;)
•open database for operation