Oracle 11g的Redo Log和Archive Log的分析方法
自Oracle 11g起，无需设置UTL_FILE_DIR就可以使用LOGMNR对本地数据库的日志进行分析，以下是使用LOGMNR的DICT_FROM_ONLINE_CATALOG分析REDO和归档日志的步骤
分析REDO日志的实验
- 创建测试表，并做DML操作。
SQL> create table t_test(id number,name varchar2(15));
Table created.
SQL> insert into t_test values(1,'stream');
1 row created.
SQL> insert into t_test values(2,'dbdream');
1 row created.
SQL> commit;
Commit complete.
SQL> update t_test set name='streamsong' where id=1;
1 row updated.
SQL> commit;
Commit complete.
SQL> delete from t_test;
2 rows deleted.
SQL> commit;
Commit complete.
- 查看REDO日志的路径。
SQL> select member from v$logfile;
MEMBER
------------------------------------------------
/u01/app/oracle/oradata/stream/STREAM/redo03.log
/u01/app/oracle/oradata/stream/STREAM/redo02.log
/u01/app/oracle/oradata/stream/STREAM/redo01.log
- 添加REDO日志
第一个添加的日志需指定NEW，如果确定要查询的信息在指定的REDO日志内，可以只添加那个REDO日志，而不需要再添加其他
SQL> exec dbms_logmnr.add_logfile(logfilename=>'/u01/app/oracle/oradata/stream/STREAM/redo01.log',options=>dbms_logmnr.new);
PL/SQL procedure successfully completed.
- 添加其他REDO日志
不是第一个添加的日志需指定ADDFILE。
SQL> exec dbms_logmnr.add_logfile(logfilename=>'/u01/app/oracle/oradata/stream/STREAM/redo02.log',options=>dbms_logmnr.addfile);
PL/SQL procedure successfully completed.
SQL> exec dbms_logmnr.add_logfile(logfilename=>'/u01/app/oracle/oradata/stream/STREAM/redo03.log',options=>dbms_logmnr.addfile);
PL/SQL procedure successfully completed.
- 开始对添加的REDO进行分析
SQL> exec dbms_logmnr.start_logmnr(options=>dbms_logmnr.dict_from_online_catalog);
PL/SQL procedure successfully completed.
- 查看LOGMNR分析后得到的信息
LOGMNR分析后的数据会存放在v$logmnr_contents视图中，通过查询v$logmnr_contents视图就可以查询到REDO日志的信息。
SQL> select timestamp,sql_redo,sql_undo from v$logmnr_contents where username='SCOTT'and table_name='T_TEST';
TIMESTAMP SQL_REDO
--------- -----------------------------------------------------------
21-MAR-12 create table t_test(id number,name varchar2(15));
21-MAR-12 insert into "SCOTT"."T_TEST"("ID","NAME") values ('1','stream');
21-MAR-12 insert into "SCOTT"."T_TEST"("ID","NAME") values ('2','dbdream');
21-MAR-12 update "SCOTT"."T_TEST" set "NAME" = 'streamsong' where "NAME" ='stream' and ROWID = 'AAAR7fAAEAAAADXAAA';
21-MAR-12 delete from "SCOTT"."T_TEST" where "ID" = '1' and "NAME" = 'streamsong' and ROWID = 'AAAR7fAAEAAAADXAAA';
21-MAR-12 delete from "SCOTT"."T_TEST" where "ID" = '2' and "NAME" ='dbdream' and ROWID = 'AAAR7fAAEAAAADXAAB';
SQL_REDO就是执行的SQL语句，SQL_UNDO是回滚操作的SQL语句，也就是执行SQL_UNDO的相关SQL，就可以回滚对应的操作。
注：LOGMNR是SESSION级的，以上实验第3步到第6步需在同一个SESSION中进行，SESSION断开连接后需重新执行，否则会报以下错误提示。
ORA-01306: dbms_logmnr.start_logmnr() must be invoked before selecting from v$logmnr_contents
- 结束LOGMNR操作
由于LOGMNR是会话级的，可以用直接退出或关闭当前的终端的方式来结束LOGMNR的操作，当然，正确的结束LOGMNR操作需使用下面的命令。
SQL> exec dbms_logmnr.end_logmnr;
PL/SQL procedure successfully completed.
分析归档日志的实验
分析归档日志的操作和分析REDO的操作基本一样，最重要的就是准确的找到需要查找的信息在哪些归档日志内。既然是利用LOGMNR分析归档日志，数据库一定是在归档模式，要不哪来的归档日志，可以通过如下命令查看数据库是否启用归档模式。
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 15
Next log sequence to archive 17
Current log sequence 17
可以看到当前数据库已经开启归档模式，归档地址是USE_DB_RECOVERY_FILE_DEST，USE_DB_RECOVERY_FILE_DEST的具体位置可以通过下面的命令查看。
SQL> show parameter db_recove
NAME TYPE VALUE
--------------------------- ----------- -------------------------------
db_recovery_file_dest string /u01/app/oracle/flash_recovery_area
db_recovery_file_dest_size big integer 3852M
如果数据据库开启闪回恢复区，闪回恢复区就是默认的归档地址，我个人建议使用这个空间存放归档日志，因为从Oracle 11g开始当该空间的使用率达到80%的时候，系统会自动删除已经备份过的归档文件，避免被撑爆。闪回恢复区的大小受db_recovery_file_dest_size大小的限制，是一个动态参数，可以随时在线修改。
本实验步骤如下：
- 切换日志，使REDO日志归档。
SQL> alter system switch logfile;
System altered.
SQL> /
System altered.
SQL> /
System altered.
- 按照归档日志的时间，找到存放需要分析信息的归档日志。
[oracle@stream 2012_03_21]$ pwd
/u01/app/oracle/flash_recovery_area/STREAM/archivelog/2012_03_21
[oracle@stream 2012_03_21]$ ll
total 32196
-rw-r----- 1 oracle oinstall 26598912 Mar 21 10:55 o1_mf_1_12_7pljs9lb_.arc
-rw-r----- 1 oracle oinstall 6206976 Mar 21 14:05 o1_mf_1_13_7plvx3bc_.arc
-rw-r----- 1 oracle oinstall 100864 Mar 21 14:07 o1_mf_1_14_7plw0bgo_.arc
-rw-r----- 1 oracle oinstall 1024 Mar 21 14:07 o1_mf_1_15_7plw0d0q_.arc
-rw-r----- 1 oracle oinstall 2048 Mar 21 14:07 o1_mf_1_16_7plw0gc1_.arc
- 将归档日志添加到LOGMNR。
SQL> exec dbms_logmnr.add_logfile(logfilename=>'/u01/app/oracle/flash_recovery_area/STREAM/archivelog/2012_03_21/o1_mf_1_13_7plvx3bc_.arc',options=>dbms_logmnr.new);
PL/SQL procedure successfully completed.
SQL> exec dbms_logmnr.add_logfile(logfilename=>'/u01/app/oracle/flash_recovery_area/STREAM/archivelog/2012_03_21/o1_mf_1_14_7plw0bgo_.arc',options=>dbms_logmnr.addfile);
PL/SQL procedure successfully completed.
- 开始分析。
SQL> exec dbms_logmnr.start_logmnr(options=>dbms_logmnr.dict_from_online_catalog);
PL/SQL procedure successfully completed.
- 查看LOGMNR分析后的数据。
SQL> select timestamp,sql_redo from v$logmnr_contents where username='SCOTT' and table_name='T_TEST';
TIMESTAMP SQL_REDO
--------- -----------------------------------------------------------------
21-MAR-12 create table t_test(id number,name varchar2(15));
21-MAR-12 insert into "SCOTT"."T_TEST"("ID","NAME") values ('1','stream');
21-MAR-12 insert into "SCOTT"."T_TEST"("ID","NAME") values ('2','dbdream');
21-MAR-12 update "SCOTT"."T_TEST" set "NAME" = 'streamsong' where "NAME" =
'stream' and ROWID = 'AAAR7fAAEAAAADXAAA';
21-MAR-12 delete from "SCOTT"."T_TEST" where "ID" = '1' and "NAME" =
'streamsong' and ROWID = 'AAAR7fAAEAAAADXAAA';
21-MAR-12 delete from "SCOTT"."T_TEST" where "ID" = '2' and "NAME" =
'dbdream' and ROWID = 'AAAR7fAAEAAAADXAAB';
6 rows selected.
- 结束LOGMNR操作。
SQL> exec dbms_logmnr.end_logmnr;
PL/SQL procedure successfully completed.
