oracle之二日志挖掘log miner

日志挖掘 log miner

6.1 log miner的作用：

数据库恢复中有时会需要对Redo log进行分析，要会使用log miner，以便确定要恢复的时间点或SCN

6.2 有两种日志挖掘方法针对DML和DDL，整理如下：

6.2.1 对语句DML进行日志挖掘：

1）添加database补充日志
SQL>ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;

//注意：通过PL/SQL包的DML的日志挖掘，这步要先执行，在此之后的DML操作才能从日志里挖到。

2）确定要分析的日志范围，添加日志，分析
SQL>execute dbms_logmnr.add_logfile(logfilename=>'归档日志',options=>dbms_logmnr.new);   //第一个要加载的日志文件

SQL>execute dbms_logmnr.add_logfile(logfilename=>'补充日志',options=>dbms_logmnr.addfile); //可以反复添加补充多个日志文件

3）执行logmnr 分析
SQL>execute dbms_logmnr.start_logmnr(options=>dbms_logmnr.dict_from_online_catalog);

4）查询分析结果，可以设置时间格式，也可以在显示方式里再确定格式.

SQL>select username,scn,timestamp,sql_redo from v$logmnr_contents where seg_name='表名';

5）关闭日志分析
SQL>execute dbms_logmnr.end_logmnr;

例
session1 sys:
11:33:20 SQL> ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;

session2 scott:
09:44:08 SQL> create table a (id int);
09:44:20 SQL> insert into a values(1);
09:44:29 SQL> update a set id=5;
09:44:45 SQL> commit;
09:44:47 SQL> delete a;           //delete这条没有commit，我们要证明uncommit的DML操作也写入了日志。

这个session2留着，换session1进入sys

session1 sys:
11:32:12 SQL> select * from v$log;

    GROUP#    THREAD# SEQUENCE#      BYTES    MEMBERS    ARCHIVED STATUS           FIRST_CHANGE#    FIRST_TIME
---------- ---------- ---------- ---------- ---------- -------- ---------------- ------------- -----------
         1             1         26     52428800          2        NO          CURRENT               2257870        2012-7-23 9
         2             1         25     52428800          2        YES         INACTIVE               2257866        2012-7-23 9
         3            1         23     52428800          2       YES         INACTIVE               2257862        2012-7-23 9
         4             1         24     52428800          2        YES         INACTIVE               2257864        2012-7-23 9

//上面a 表的DML操作都写进了current组里，记住sequence#是26号。然后手工切换当前日志到archive里。

11:32:18 SQL> alter system switch logfile;
11:33:00 SQL> /
11:33:02 SQL> /
11:33:02 SQL> /

11:33:09 SQL> select name from v$archived_log;

/u01/disk1/timran/arch_1_789252862_21.log
/u01/disk1/timran/arch_1_789252862_22.log
/u01/disk1/timran/arch_1_789252862_23.log
/u01/disk1/timran/arch_1_789252862_24.log
/u01/disk1/timran/arch_1_789252862_25.log
/u01/disk1/timran/arch_1_789252862_26.log
/u01/disk1/timran/arch_1_789252862_27.log
/u01/disk1/timran/arch_1_789252862_28.log
/u01/disk1/timran/arch_1_789252862_29.log

62 rows selected

//切换后，sequence#26的日志的应该对应的是/u01/disk1/timran/arch_1_789252862_26.log

11:33:48 SQL> execute dbms_logmnr.add_logfile(logfilename=>'/u01/data/urpdb/redo03.log',options=>dbms_logmnr.new);

11:34:13 SQL> execute dbms_logmnr.start_logmnr(options=>dbms_logmnr.dict_from_online_catalog);

11:34:49 SQL>select scn,to_char(timestamp,'yyyy-mm-dd hh24:mi:ss') timestamp,sql_redo from v$logmnr_contents where seg_name='AA';

       SCN TIMESTAMP           SQL_REDO
---------- ------------------- --------------------------------------------------------------------------------
   2258232 2012-07-23 09:43:16 drop table a purge;
   2258334 2012-07-23 09:44:20 create table a (id int);
   2258341 2012-07-23 09:44:28 insert into "SCOTT"."A"("ID") values ('1');
   2258349 2012-07-23 09:44:46 update "SCOTT"."A" set "ID" = '5' where "ID" = '1' and ROWID = 'AAANBAAAEAAAAGEA
   2258353 2012-07-23 09:44:52 delete from "SCOTT"."A" where "ID" = '5' and ROWID = 'AAANBAAAEAAAAGEAAA';

6.2.2 对DDL的操作的log miner：

1）如果是第一次做，先要建好logmnr目录，

设置logmnr 参数，存放数据字典文件dict01.ora
$ mkdir /home/oracle/logmnr

SQL> alter system set utl_file_dir='/home/oracle/logmnr' scope=spfile;

2）建立数据字典文件dict.ora
SQL> execute dbms_logmnr_d.build('dict01.ora','/home/oracle/logmnr',dbms_logmnr_d.store_in_flat_file);

3）添加日志分析
SQL> alter system switch logfile;

SQL> execute dbms_logmnr.add_logfile(logfilename=>'归档文件',options=>dbms_logmnr.new);
SQL> execute dbms_logmnr.add_logfile(logfilename=>'归档文件',options=>dbms_logmnr.addfile);

4）执行分析
SQL> execute dbms_logmnr.start_logmnr(dictfilename=>'/home/oracle/logmnr/dict01.ora',options=>dbms_logmnr.ddl_dict_tracking);
5）查看分析结果

SQL> select username,scn,to_char(timestamp,'yyyy-mm-dd hh24:mi:ss'),sql_redo from v$logmnr_contents WHERE USERNAME ='SCOTT' and lower(sql_redo) like '%table%';

6）关闭日志分析
SQL> execute dbms_logmnr.end_logmnr;

例子将在053的不完全恢复一节中演示。

在oracle11g 的EM里已加入了有关log miner的功能，可根据时间段由oracle自动选择需要的日志，比较方便，但只有提交的事务信息，看来是从transaction的角度设计的。

EM-->Availability-->Manage-->View and Manage Transctions

oracle之二日志挖掘log miner

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