LogMiner是Oracle数据库提供的一个工具，它用于分析重做日志和归档日志所记载的事务操作。
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Logminer是oracle从8i开始提供的用于分析重做日志信息的工具，它包括DBMS_LOGMNR和DBMS_LOGMNR_D两个package。它既能分析redo log file，也能分析归档后的archive log file。在分析日志的过程中需要使用数据字典，一般先生成数据字典文件后使用，10g版本还可以使用在线数据字典。
Logminer也可以分析其它数据库的重做日志文件，但是必须使用重做日志所在数据库的数据字典，否则会出现无法识别的乱码。另外被分析数据库的操作系统平台最好和当前Logminer所在数据库的运行平台一样，且block size相同。
LogMiner的功能
1）确定数据库的逻辑损坏时间
通过LogMiner可以准确定位该误操作的执行时间和SCN值，然后通过基于时间恢复或者基于SCN恢复可以完全恢复该表数据。
SQL> select scn_to_timestamp(2599788) from dual;
scn_to_timestamp(2599788)
-------------------
2016-05-01 06:06:01
SQL>select timestamp_to_scn(to_timestamp('2016-5-1 6:06:06','yyyy-mm-dd hh34:mi:ss')) FROM dual;
TIMESTAMP_TO_SCN(TO_TIMESTAMP('2016-5-16:06:06','YYYY-MM-DDHH24:MI:SS'))
------------------------------------------------------------------------
2599788
2）确定事务级要执行的精细逻辑恢复操作
通过LogMiner可以取得任何用户的DML操作及相应的UNDO操作，通过执行UNDO操作可以取消用户的错误操作。
3）执行后续审计
通过LogMiner可以跟踪Oracle数据库的所有DML、DDL和DCL操作，从而取得执行这些操作的时间顺序、执行这些操作的用户等信息。
追加日志
重做日志用于实现例程恢复和介质恢复，这些操作所需要的数据被自动记录在重做日志中。但是，重做应用可能还需要记载其他列信息到重做日志中，记录其他列的日志过程被称为追加日志。
默认情况下，Oracle数据库没有开启追加日志，从而导致默认情况下LogMiner无法支持以下特征：
1）索引簇、链行和迁移行；
2）直接路径插入；
3）摘取LogMiner字典到重做日志；
4）跟踪DDL；
5）生成键列的SQL_REDO和SQL_UNDO信息；
6）LONG和LOB数据类型。
----如何修改追加日志数据模式：
SYS@test> select supplemental_log_data_min from v$database;
SUPPLEME
--------
NO
SYS@test> alter database add supplemental log data;
Database altered.
SYS@test> select supplemental_log_data_min from v$database;
SUPPLEME
--------
YES
----关闭追加日志
SYS@test> alter database drop supplemental log data;
Database altered.
SYS@test> select supplemental_log_data_min from v$database;
SUPPLEME
--------
NO
SYS@test> create user shall identified by shall;
User created.
SYS@test> grant connect,resource to shall;
Grant succeeded.
SHALL@test> create table test(id number,name varchar2(20));
Table created.
SHALL@test> begin
2 for i in 1..100000 loop
3 insert into test values(i,'zhong');
4 end loop;
5 commit;
6 end;
7 /
PL/SQL procedure successfully completed.
SHALL@test> select count(*) from test;
COUNT(*)
----------
100000
SHALL@test> select * from test where id = 999;
ID NAME
---------- --------------------
999 zhong
SHALL@test> delete test;
100000 rows deleted.
SHALL@test> commit;
Commit complete.
SHALL@test> select * from test;
no rows selected
SYS@test> select supplemental_log_data_min from v$database;
SUPPLEME
--------
NO
SYS@test> select member from v$logfile;
MEMBER
--------------------------------------------------------------------------------
/u01/app/oracle/oradata/orcl/redo01_1.log
/u01/app/oracle/oradata/orcl/redo02_1.log
/u01/app/oracle/oradata/orcl/redo03_1.log
SYS@test> exec dbms_logmnr.add_logfile ('/u01/app/oracle/oradata/orcl/redo01_1.log');
PL/SQL procedure successfully completed.
SYS@test> exec dbms_logmnr.add_logfile ('/u01/app/oracle/oradata/orcl/redo02_1.log');
PL/SQL procedure successfully completed.
SYS@test> exec dbms_logmnr.add_logfile ('/u01/app/oracle/oradata/orcl/redo03_1.log');
PL/SQL procedure successfully completed.
----如果刚做了误操作，日志未切换，可以只添加当前redo
SYS@test> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 INACTIVE
2 INACTIVE
3 CURRENT
SYS@test> col member for a50
SYS@test> select group#,member,type from v$logfile;
GROUP# MEMBER TYPE
---------- -------------------------------------------------- -------
1 /u01/app/oracle/oradata/orcl/redo01_1.log ONLINE
2 /u01/app/oracle/oradata/orcl/redo02_1.log ONLINE
3 /u01/app/oracle/oradata/orcl/redo03_1.log ONLINE
SYS@test> exec dbms_logmnr.start_logmnr(options=>dbms_logmnr.dict_from_online_catalog);
PL/SQL procedure successfully completed.
SYS@test> select sql_redo from v$logmnr_contents where lower(sql_redo) like '%delete%' and seg_name='TEST';
redo数据如下：
SQL_REDO
--------------------------------------------------------------------------------
delete from "SHALL"."TEST" where "ID" = '42016' and "NAME" = 'zhong' and ROWID =
'AAAWGEAAEAAAOSfABL';
delete from "SHALL"."TEST" where "ID" = '42017' and "NAME" = 'zhong' and ROWID =
'AAAWGEAAEAAAOSfABM';
delete from "SHALL"."TEST" where "ID" = '42018' and "NAME" = 'zhong' and ROWID =
'AAAWGEAAEAAAOSfABN';
delete from "SHALL"."TEST" where "ID" = '42019' and "NAME" = 'zhong' and ROWID =
undo数据如下：
SYS@test> select sql_redo from v$logmnr_contents where lower(sql_undo) like '%delete%' and seg_name='TEST';
SQL_REDO
--------------------------------------------------------------------------------
insert into "SHALL"."TEST"("ID","NAME") values ('5039','zhong');
insert into "SHALL"."TEST"("ID","NAME") values ('5040','zhong');
insert into "SHALL"."TEST"("ID","NAME") values ('5041','zhong');
insert into "SHALL"."TEST"("ID","NAME") values ('5042','zhong');
insert into "SHALL"."TEST"("ID","NAME") values ('5043','zhong');
insert into "SHALL"."TEST"("ID","NAME") values ('5044','zhong');
insert into "SHALL"."TEST"("ID","NAME") values ('5045','zhong');
insert into "SHALL"."TEST"("ID","NAME") values ('5046','zhong');
SYS@test> set linesize 200
SYS@test> set pagesize 10000
SYS@test> create table shall as select sql_redo from v$logmnr_contents where lower(sql_undo) like '%delete%' and seg_name='TEST';
SYS@test> select * from shall;
SYS@test> EXECUTE DBMS_LOGMNR.END_LOGMNR;
PL/SQL procedure successfully completed.
