Flashback Version Query

时间  2020-06-22
标签 flashback version query 栏目 Flash 繁體版
原文   原文链接

 

09:23:45 SCOTT@db252>select * from dept;sql

DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON数据库

Elapsed: 00:00:00.04
09:23:57 SCOTT@db252>insert into dept values(50,'WHAT\'S THAT','BEIJING');
ERROR:
ORA-01756: quoted string not properly terminatedoracle


Elapsed: 00:00:00.06
09:24:38 SCOTT@db252>insert into dept values(50,q'[WHAT'S THAT]','BEIJING');ui

1 row created.spa

Elapsed: 00:00:00.04
09:25:13 SCOTT@db252>commit;.net

Commit complete.blog

Elapsed: 00:00:00.00
09:25:16 SCOTT@db252>select * from dept;事务

DEPTNO DNAME LOC
---------- -------------- -------------
50 WHAT'S THAT BEIJING
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTONip

Elapsed: 00:00:00.02ci

09:29:10 SCOTT@db252>select * from dept versions between timestamp to_timestamp('2014-06-06 09:10:48','yyyy-mm-dd hh24:mi:ss') and to_timestamp('2014-
06-06 09:26:48','yyyy-mm-dd hh24:mi:ss');

DEPTNO DNAME LOC
---------- -------------- -------------
50 WHAT'S THAT BEIJING
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON

Elapsed: 00:00:00.05
09:32:26 SCOTT@db252>select * from dept versions between timestamp to_timestamp('2014-06-06 09:10:48','yyyy-mm-dd hh24:mi:ss') and to_timestamp('2014-
06-06 09:12:48','yyyy-mm-dd hh24:mi:ss');

DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON

Elapsed: 00:00:00.02
09:32:39 SCOTT@db252>

 

 

flashback六大技术之flashback version query

环境：

[sql]  view plain copy print ?
 
  1. 23:47:03 hr@ORCL (^ω^) select * from v$version where rownum=1;  
  2.   
  3. BANNER  
  4. --------------------------------------------------------------------------------  
  5. Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod  


    1 原理介绍

        flashback query只能“穿越”到过去的某个时间点上的数据库版本，可是在当前时间和过去的某个时间点上，一个表中的数据可能已经被变动屡次，单一版本可能没法知足恢复的需求。经过flashback version query可以查看指定时间段内undo表空间中被提交的记录的不一样版本。

                                flashback version query的伪列说明

 

 

versions_startscn

versions_starttime

 记录了操做时的SCN或时间，若是为空，表示在查询范围外建立的

versions_endscn

versions_endtime

记录了失效时的SCN或时间，配合version_operation列查看，若是为空，或者被删除、或者

该记录当前时间在当前表不存在
versions_operation I：insert     D：delete    U：update
versions_operation 事务ID

 

 

    2 实验

[sql]  view plain copy print ?
 
    1. 23:38:26 hr@ORCL (^ω^) select dbms_flashback.get_system_change_number from dual;  
    2.   
    3. GET_SYSTEM_CHANGE_NUMBER  
    4. ------------------------  
    5.                  3930808  
    6.   
    7. 23:38:48 hr@ORCL (^ω^) update t1 set empno=122 where ename='Water';  
    8.   
    9. 已更新 1 行。  
    10.   
    11. 23:39:42 hr@ORCL (^ω^) commit;  
    12.   
    13. 提交完成。  
    14.   
    15. 23:40:06 hr@ORCL (^ω^) delete t1 where rownum<5;  
    16.   
    17. 已删除4行。  
    18.   
    19. 23:40:25 hr@ORCL (^ω^) commit;  
    20.   
    21. 提交完成。  
    22.   
    23. 23:40:29 hr@ORCL (^ω^) insert into t1 values(155,'qao');  
    24.   
    25. 已建立 1 行。  
    26.   
    27. 23:40:56 hr@ORCL (^ω^) insert into t1 values(156,'qinqin');  
    28.   
    29. 已建立 1 行。  
    30.   
    31. 23:41:19 hr@ORCL (^ω^) commit;  
    32.   
    33. 提交完成。  
    34.   
    35. 23:41:22 hr@ORCL (^ω^) select dbms_flashback.get_system_change_number from dual;  
    36.   
    37. GET_SYSTEM_CHANGE_NUMBER  
    38. ------------------------  
    39.                  3931066  
    40.   
    41. 23:46:34 hr@ORCL (^ω^) select empno,ename,versions_startscn,versions_endscn,versions_operation,versions_xid  
    42. 23:47:00   2              from t1 versions between scn 3930808 and 3931066;  
    43.   
    44.      EMPNO ENAME      VERSIONS_STARTSCN VERSIONS_ENDSCN VE VERSIONS_XID  
    45. ---------- ---------- ----------------- --------------- -- ----------------  
    46.        155 qao                  3930985                 I  04002000D4030000  
    47.        111 Linshuibin           3930897                 D  06002F00B6040000  
    48.        122 Water                3930897                 D  06002F00B6040000  
    49.        122 Water                3930883         3930897 U  02001100BD040000  
    50.        111 Water                                3930883  
    51.        111 Linshuibin                           3930897  
    52.       7566 JONES                3930897                 D  06002F00B6040000  
    53.       7521 WARD                 3930897                 D  06002F00B6040000  
    54.       7521 WARD                                 3930897  
    55.       7566 JONES                                3930897  
    56.       7788 SCOTT  
    57.       7844 TURNER  
    58.       7900 JAMES  
    59.       7902 FORD  
    60.        156 qinqin               3930985                 I  04002000D4030000  
    61.        110 Think  
    62.   
    63. 已选择16行。  

 

 

关于flashback versions query 和flashback transaction query 特性

前面提到了oracle 自9i以来的flashback query 特性，借助该特性，能够看到某个过去某个时间点的某张表的数据，这为咱们修正dml 误操做等提供了很大的方便。
可是对于该特性来讲，若是只是想回退某个时间点以来的部分数据，那么纯粹依靠先后的数据对比来判断，就会显的很是吃力，或许根本就是没法办到的。好比，你某时刻同时跑起了多个job做业，
若是一个job有问题，而其余的job正常完成的，此时，若是你仅仅是想回复错误job处理过的数据，而要保留正常job的处理结果，可是或许你没法判断后面变化的数据哪些是正常job的，哪些是错误job的，所以，很难进行部分数据的修复工做。


   10g提供了flashback versions query 和 flashback transaction query 特性，它强化了9i 的flashback query 特性，正是解决上面相似问题的利器。
   
1.flashback versions query
   flashback versions query 可以获得某个时间段内，某些数据行的全部不一样版本。这里的版本以事务为单位，事务中的每次数据变化就是一个版本。
举例说明，下面的会话2次update id=1 时的 name 值，所以分别提交过2次，所以是2个不一样的事务，在flashback versions query 的结果中，关于
id=1 ，咱们看到了3个不一样的版本，一个是原来的值，一个是第一次修改的值，一个是第二次修改的值；经过flashback versions query 中的versions_startscn,versions_starttime
versions_endscn, versions_endtime,versions_xid, versions_operation 等伪列，咱们也得到了相关版本的开始scn，结束scn，开始时间和结束时间，以及作dml操做的具体transaction id (xid)，以及操做类型等；
同时，咱们也看到对于id=1的数据行，三个版本的VERSIONS_ENDSCN,VERSIONS_ENDtime 和 VERSIONS_startscn，VERSIONS_starttime 是承上启下的，一个版本的结束，也就是下一个版本的开始。


15:37:22 SQL> select *  from test;

        ID NAME
---------- --------------------
         1 kkk
         2 fff
         4 kkk

Executed in 0.031 seconds

15:37:34 SQL> update   test set name='TEST' where id=1;

1 row updated

Executed in 0.015 seconds

15:37:54 SQL> commit;

Commit complete

Executed in 0 seconds

15:37:56 SQL> update   test set name='TEST_new' where id=1;

1 row updated

Executed in 0.015 seconds

15:38:04 SQL> commit;

Commit complete

Executed in 0 seconds

15:38:06 SQL> 
15:39:12 SQL> SELECT versions_startscn, versions_starttime,
           2                      versions_endscn, versions_endtime,
           3                      versions_xid, versions_operation,
           4                      id,name
           5                 FROM test
           6               VERSIONS BETWEEN TIMESTAMP
           7                     TO_TIMESTAMP('2008-04-27 15:37:30', 'YYYY-MM-DD HH24:MI:SS')
           8               AND TO_TIMESTAMP('2008-04-27 15:38:30', 'YYYY-MM-DD HH24:MI:SS')
           9  ;

VERSIONS_STARTSCN VERSIONS_STARTTIME                                                               VERSIONS_ENDSCN VERSIONS_ENDTIME                                                                 VERSIONS_XID     VERSIONS_OPERATION         ID NAME
----------------- -------------------------------------------------------------------------------- --------------- -------------------------------------------------------------------------------- ---------------- ------------------ ---------- --------------------
           819393 27-4月 -08 03.38.06 下午                                                                                                                                                          040015006F010000 U                           1 TEST_new
           819387 27-4月 -08 03.37.54 下午                                                                  819393 27-4月 -08 03.38.06 下午                                                         0500150088010000 U                           1 TEST
                                                                                                            819387 27-4月 -08 03.37.54 下午                                                                                                      1 kkk
                                                                                                                                                                                                                                                 2 fff
                                                                                                                                                                                                                                                 4 kkk

Executed in 0.031 seconds

15:39:13 SQL> select *  from test;

        ID NAME
---------- --------------------
         1 TEST_new
         2 fff
         4 kkk

Executed in 0 seconds

15:43:52 SQL> 


2. flashback transaction query
    flashback transaction query 其实就是查询历史的事务信息，经过查询，咱们能够获得过去某个事务操做信息，包括改变的数据行rowid，事务开始和结束时间，事务对应的loggon user，以及用来撤销某个数据行改变的undo sql等。
flashback transaction query 其实就是查询 FLASHBACK_TRANSACTION_QUERY 视图。

好比，经过上面 versions query 获得的xid，咱们能够获得这些xid 对应的信息。


15:43:52 SQL> SELECT xid, operation, start_scn,commit_scn, logon_user, undo_sql  FROM flashback_transaction_query  WHERE xid = HEXTORAW('&1');

XID              OPERATION                         START_SCN COMMIT_SCN LOGON_USER                     UNDO_SQL
---------------- -------------------------------- ---------- ---------- ------------------------------ --------------------------------------------------------------------------------
040015006F010000 UPDATE                               819387     819393 TEST1                          update "TEST1"."TEST" set "NAME" = 'TEST' where ROWID = 'AAAM1/AAEAAAAGsAAA';
040015006F010000 BEGIN                                819387     819393 TEST1                          

Executed in 0.297 seconds

15:57:34 SQL> SELECT xid, operation, start_scn,commit_scn, logon_user, undo_sql  FROM flashback_transaction_query  WHERE xid = HEXTORAW('&1');

XID              OPERATION                         START_SCN COMMIT_SCN LOGON_USER                     UNDO_SQL
---------------- -------------------------------- ---------- ---------- ------------------------------ --------------------------------------------------------------------------------
0500150088010000 UPDATE                               819184     819387 TEST1                          update "TEST1"."TEST" set "NAME" = 'kkk' where ROWID = 'AAAM1/AAEAAAAGsAAA';
0500150088010000 BEGIN                                819184     819387 TEST1                          

Executed in 0.032 seconds

15:58:07 SQL> 


3.一个例子
flashback versions query 和flashback transaction query 通常都是结合起来用的，经过前者获得某个时间段的某些数据的多个版本的xid，而后经过后者获得具体的xid的操做信息及undo_sql，最后根据须要作适当的数据修复操做。


SQL> create table  test  (id number ,name varchar2(20));

Table created

SQL> set time on
14:55:14 SQL> set timing on
14:55:18 SQL> insert into test values ( 1,'kkk');

1 row inserted

Executed in 0.016 seconds

14:55:27 SQL> insert into test values ( 2,'fff');

1 row inserted

Executed in 0.016 seconds

14:55:34 SQL> commit;

Commit complete

Executed in 0 seconds

14:55:39 SQL> 


此时打开第二个会话窗口，执行以下：
SQL> insert into test1.test values ( 4,'kkk');

1 row inserted

SQL> commit;

Commit complete

SQL>

--再回到第一个窗口，进行 flashback versions query 

15:00:20 SQL> SELECT versions_startscn, versions_starttime,
           2         versions_endscn, versions_endtime,
           3         versions_xid, versions_operation,
           4         id,name
           5    FROM test
           6  VERSIONS BETWEEN TIMESTAMP
           7        TO_TIMESTAMP('2008-04-27 14:55:20', 'YYYY-MM-DD HH24:MI:SS')
           8  AND TO_TIMESTAMP('2008-04-27 14:57:00', 'YYYY-MM-DD HH24:MI:SS')
           9  ;

VERSIONS_STARTSCN VERSIONS_STARTTIME                                                               VERSIONS_ENDSCN VERSIONS_ENDTIME                                                                 VERSIONS_XID     VERSIONS_OPERATION         ID NAME
----------------- -------------------------------------------------------------------------------- --------------- -------------------------------------------------------------------------------- ---------------- ------------------ ---------- --------------------
           817371 27-4月 -08 02.55.39 下午                                                                                                                                                          0900070081010000 I                           2 fff
           817371 27-4月 -08 02.55.39 下午                                                                                                                                                          0900070081010000 I                           1 kkk
           817386 27-4月 -08 02.56.03 下午                                                                                                                                                          0700280072010000 I                           4 kkk

Executed in 0.016 seconds

15:00:21 SQL> 


-- flashback  transaction query 
15:00:21 SQL> SELECT xid, operation, start_scn,commit_scn, logon_user, undo_sql  FROM flashback_transaction_query  WHERE xid = HEXTORAW('&1');

XID              OPERATION                         START_SCN COMMIT_SCN LOGON_USER                     UNDO_SQL
---------------- -------------------------------- ---------- ---------- ------------------------------ --------------------------------------------------------------------------------
0900070081010000 INSERT                               817359     817371 TEST1                          delete from "TEST1"."TEST" where ROWID = 'AAAM1/AAEAAAAGsAAB';
0900070081010000 INSERT                               817359     817371 TEST1                          delete from "TEST1"."TEST" where ROWID = 'AAAM1/AAEAAAAGsAAA';
0900070081010000 BEGIN                                817359     817371 TEST1                          

Executed in 0.593 seconds

15:03:54 SQL> 
15:11:27 SQL> 
15:11:27 SQL> 
15:11:27 SQL> SELECT xid, operation, start_scn,commit_scn, logon_user, undo_sql  FROM flashback_transaction_query  WHERE xid = HEXTORAW('&1');

XID              OPERATION                         START_SCN COMMIT_SCN LOGON_USER                     UNDO_SQL
---------------- -------------------------------- ---------- ---------- ------------------------------ --------------------------------------------------------------------------------
0700280072010000 INSERT                                    0     817386 TEST2                          delete from "TEST1"."TEST" where ROWID = 'AAAM1/AAEAAAAGwAAA';
0700280072010000 BEGIN                                     0     817386 TEST2                          

Executed in 0.031 seconds

15:11:47 SQL> 

4.undo_rentention

和9i flashback query 同样，flashback  versions query和flashback  transaction query 也都是依赖于undo tablespace，依赖于undo_retention 的。换句话说，对于已经不存在于undo tablespace 的数据版本信息，
你固然是没法经过 这些特性把它查出来的。所以设置好undo tablespace 的大小，设置好undo_rentention 的大小就尤其重要(10g 虽然有自动tuning undo_retention 的功能，不过考量并设置合适的undo_retention 最小值也是颇有必要的）

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