--- 说明闪回数据库
--- 使用闪回表将表内容还原到过去的特定时间点
--- 从删除表中进行恢复
--- 使用闪回查询查看截止到任一时间点的数据库内容
--- 使用闪回版本查询查看某一行在一段时间内的各个版本
--- 使用闪回事务查询查看事务处理历史记录或行
优点：
闪回技术由于只能处理更改数据，所以从根本上改变了恢复技术。使用这个技术时，从错误中恢复花费的时间等于制造错误所花费的时间。当闪回技术使用时，它与介质恢复相比，在易用性、可用性和还原时间方面有明显的优势。
闪回数据库使用闪回日志执行闪回。闪回删除使用回收站。其他所有功能都使用还原数据。
闪回时间浏览
闪回技术提供的功能可用于查询方案对象的过去版本、查询历史记录数据以及执行更改分析。每个事务处理在逻辑上都会生成新版本数据库。使用闪回技术，可通过浏览这些版本来查找错误以及原因。
· 闪回查询：查询特定时间点的所有数据。
· 闪回版本查询：查看两个时间之间行的所有版本已经更改了行的事务处理。
· 闪回事务处理查询：查看事务处理做的所有更改。
使用闪回查询功能时，可以对自特定时间起的数据库执行查询。通过使用select语句的 as of 子句，可指定要查看其数据的时间戳。这有助于分析数据差异。
实验一：闪回查询
实验一：闪回查询：as of timestamp
SYS@ORCL>conn tyger/tyger
Connected.
TYGER@ORCL>create table fb_query as select * from scott.dept;
Table created.
TYGER@ORCL>select * from fb_query;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
TYGER@ORCL>set time on;
09:51:36 TYGER@ORCL>delete fb_query where deptno=10;
1 row deleted.
09:51:53 TYGER@ORCL>commit;
Commit complete.
09:51:57 TYGER@ORCL>select * from fb_query;
DEPTNO DNAME LOC
---------- -------------- -------------
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
09:52:06 TYGER@ORCL>select * from fb_query as of timestamp sysdate-1/1440;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
实验二：闪回查询应用
10:25:04 TYGER@ORCL>drop table fb_tyger purge;
Table dropped.
10:25:10 TYGER@ORCL>create table fb_tyger as select * from scott.dept;
Table created.
10:25:33 TYGER@ORCL>select * from fb_tyger;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
10:25:44 TYGER@ORCL>select sysdate from dual;
SYSDATE
---------
14-MAR-14
10:26:02 TYGER@ORCL>alter session set nls_date_format=‘yyyy-mm-dd hh24:mi:ss‘;
Session altered.
10:26:30 TYGER@ORCL>select sysdate from dual;
SYSDATE
-------------------
2014-03-14 10:26:38
10:26:38 TYGER@ORCL>update fb_tyger set dname=‘‘;
4 rows updated.
10:26:51 TYGER@ORCL>commit;
Commit complete.
10:26:54 TYGER@ORCL>select * from fb_tyger;
DEPTNO DNAME LOC
---------- -------------- -------------
10 NEW YORK
20 DALLAS
30 CHICAGO
40 BOSTON
10:27:12 TYGER@ORCL>select * from fb_tyger as of timestamp to_timestamp(‘2014-03-14 10:26:38‘,‘yyyy-mm-dd hh24:mi:ss‘);
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
此处遇到错误：
ERROR at line 1:
ORA-01466: unable to read data - table definition has changed
参考文档： http://blog.csdn.net/wanghui5767260/article/details/21227101
10:29:21 TYGER@ORCL>select * from fb_tyger as of timestamp sysdate-3/1440;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
10:29:35 TYGER@ORCL>select * from fb_tyger;
DEPTNO DNAME LOC
---------- -------------- -------------
10 NEW YORK
20 DALLAS
30 CHICAGO
40 BOSTON
10:46:22 TYGER@ORCL>set time off
TYGER@ORCL>update fb_tyger t
2 set dname =
3 (select dname from fb_tyger as of timestamp
4 to_timestamp(‘2014-03-14 10:26:38‘,‘yyyy-mm-dd hh24:mi:ss‘)
5 where t.deptno=fb_tyger.deptno);
4 rows updated.
TYGER@ORCL>commit;
Commit complete.
TYGER@ORCL>select * from fb_tyger;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
实验三：闪回查询 as of scn
TYGER@ORCL>conn / as sysdba
Connected.
SYS@ORCL>grant execute on dbms_flashback to tyger;
Grant succeeded.
TYGER@ORCL>select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
1107246
TYGER@ORCL>select * from fb_tyger;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
TYGER@ORCL>delete fb_tyger where deptno<=30;
3 rows deleted.
TYGER@ORCL>commit;
Commit complete.
TYGER@ORCL>select * from fb_tyger;
DEPTNO DNAME LOC
---------- -------------- -------------
40 OPERATIONS BOSTON
TYGER@ORCL>select * from fb_tyger as of scn 1107246;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
实验四：利用PL/SQL包dbms_flashback
语法：
· 会话启用闪回指定时间：
DBMS_FLASHBACK.ENABLE_AT_TIME(query_time IN TIMESTAMP)；
· 会话启用闪回指定SCN：
DBMS_FLASHBACK.ENABLE_AT_SYSTEM_CHANGE_NUMBER(query_scn IN NUMBER)；
· 关闭闪回：
DBMS_FLASHBACK.DISABLE；
TYGER@ORCL>conn / as sysdba
Connected.
SYS@ORCL>grant execute on dbms_flashback to tyger;
Grant succeeded.
SYS@ORCL>conn tyger/tyger
Connected.
TYGER@ORCL>
TYGER@ORCL>
TYGER@ORCL>
TYGER@ORCL>create table fb_query1 as select * from scott.dept;
Table created.
TYGER@ORCL>create table fb_query2 as select * from scott.dept;
Table created.
TYGER@ORCL>commit;
Commit complete.
TYGER@ORCL>select * from fb_query1;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
TYGER@ORCL>select * from fb_query2;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
TYGER@ORCL>set time on;
11:03:38 TYGER@ORCL>update fb_query1 set loc=‘‘;
4 rows updated.
11:03:52 TYGER@ORCL>commit;
Commit complete.
11:03:54 TYGER@ORCL>update fb_query2 set dname=‘‘;
4 rows updated.
11:04:14 TYGER@ORCL>commit;
Commit complete.
11:04:15 TYGER@ORCL>
11:04:15 TYGER@ORCL>select * from fb_query1;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING
20 RESEARCH
30 SALES
40 OPERATIONS
11:04:23 TYGER@ORCL>select * from fb_query2;
DEPTNO DNAME LOC
---------- -------------- -------------
10 NEW YORK
20 DALLAS
30 CHICAGO
40 BOSTON
// 闪回定位到5分钟前，此时若访问sysdate等时间函数，那么返回的是当前值而非5分钟之前。
11:04:30 TYGER@ORCL>exec dbms_flashback.enable_at_time(sysdate-5/1440);
PL/SQL procedure successfully completed.
11:05:09 TYGER@ORCL>select * from fb_query1;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
11:05:29 TYGER@ORCL>select * from fb_query2;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
//处于闪回会话模式时，不允许执行DML 、 DDL 操作
11:05:45 TYGER@ORCL>update fb_query1 set dname=‘‘;
update fb_query1 set dname=‘‘
*
ERROR at line 1:
ORA-08182: operation not supported while in Flashback mode
11:05:59 TYGER@ORCL>exec dbms_flashback.disable;
PL/SQL procedure successfully completed.
11:06:18 TYGER@ORCL>select * from fb_query1;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING
20 RESEARCH
30 SALES
40 OPERATIONS
11:06:30 TYGER@ORCL>select * from fb_query2;
DEPTNO DNAME LOC
---------- -------------- -------------
10 NEW YORK
20 DALLAS
30 CHICAGO
40 BOSTON
11:06:37 TYGER@ORCL>update fb_query1 set dname=‘‘ where deptno=10;
1 row updated.
11:07:10 TYGER@ORCL>select * from fb_query1;
DEPTNO DNAME LOC
---------- -------------- -------------
10
20 RESEARCH
30 SALES
40 OPERATIONS
// sys 用户不允许使用dbms_flashback 包
11:07:20 TYGER@ORCL>conn / as sysdba
Connected.
11:07:35 SYS@ORCL>set time off
SYS@ORCL>exec dbms_flashback.enable_at_time(sysdate-5/1440);
BEGIN dbms_flashback.enable_at_time(sysdate-5/1440); END;
*
ERROR at line 1:
ORA-08185: Flashback not supported for user SYS
ORA-06512: at "SYS.DBMS_FLASHBACK", line 3
ORA-06512: at line 1
实验二：闪回版本
---通过闪回版本可审计表行，检索影响行的事务处理的有关信息。然后可使用返回的事务处理标识符来执行事务处理挖掘（通过使用LogMiner）或执行闪回版本查询。
所谓版本（version）指的是每次事务所引起的数据行的变化情况，每次变化就是一个版本，oracle提供了闪回版本查询，从而可以让让我们很清楚地看到数据行的整个变化过程，这里的变化都是已经提交了的事务引起的变化，没有提交的事务引起的变化不会显示，闪回版本查询利用的是undo表空间里记录的undo数据。
使用伪列 获取一段时间内的版本
伪列：versions_starttime、versions_endtime、versions_startscn、versions_endscn、versions_xid、versions_operation、
versions_startscn versions_starttime
操作时的SCN和时间 如果为空 表示该行在查询范围之外创建
versions_endscn versions_endtime
失效时的SCN和时间 如果为空 表示该行被删除或在查询范围内无改动
versions_xid
事务ID
versions_operation
该行被执行的操作 I（insert） D(delete) U(update)
minvalue maxvalue
版本的最大时间值和最小时间值
注意事项：
versions子句不能用于查询以下特殊表：
· 外部表
· 临时表
· 固定表（x$开头的表，也就是oracle内部的表，用于数据字典的基表），下面sql语句可查询相关表
select * from v$fixed_table
不能使用versions子句查询视图。但是，在视图定义中可使用versions子句。
· versions子句不能跨DDL命令使用
· 过滤掉段收缩操作过的行
实验：闪回版本查询
TYGER@ORCL>create table tyger as select ename,job,sal from scott.emp where rownum<5;
Table created.
TYGER@ORCL>select * from tyger;
ENAME JOB SAL
---------- --------- ----------
SMITH CLERK 857
ALLEN SALESMAN 1656
WARD SALESMAN 1306
JONES MANAGER 3031
TYGER@ORCL>alter session set nls_date_format=‘yyyy-mm-dd hh24:mi:ss‘;
Session altered.
TYGER@ORCL>select sysdate from dual;
SYSDATE
-------------------
2014-03-14 14:41:46
TYGER@ORCL>update tyger set sal=sal+100 where ename=‘SMITH‘;
1 row updated.
TYGER@ORCL>commit;
Commit complete.
TYGER@ORCL>update tyger set sal=sal+100 where ename=‘SMITH‘;
1 row updated.
TYGER@ORCL>commit;
Commit complete.
TYGER@ORCL>update tyger set sal=sal+100 where ename=‘SMITH‘;
1 row updated.
TYGER@ORCL>commit;
Commit complete.
TYGER@ORCL>select * from tyger;
ENAME JOB SAL
---------- --------- ----------
SMITH CLERK 1157
ALLEN SALESMAN 1656
WARD SALESMAN 1306
JONES MANAGER 3031
TYGER@ORCL>col starttime for a30
TYGER@ORCL>l
1 select to_char(versions_starttime,‘yyyy-mm-dd hh24:mi:ss‘) as starttime,
2 versions_xid,ename,job,sal
3 from tyger versions between timestamp to_date(‘2014-03-14 14:41:46‘,‘yyyy-mm-dd hh24:mi:ss‘)
4* and sysdate where ename=‘SMITH‘
TYGER@ORCL>/
STARTTIME VERSIONS_XID ENAME JOB SAL
------------------------------ ---------------- ---------- --------- ----------
2014-03-14 14:42:32 080016000F020000 SMITH CLERK 1157
2014-03-14 14:42:26 01002C00F1010000 SMITH CLERK 1057
2014-03-14 14:42:17 0600180025020000 SMITH CLERK 957
SMITH CLERK 857
或者
TYGER@ORCL>col versions_starttime for a22
TYGER@ORCL>col versions_endtime for a22
TYGER@ORCL>l
1 select versions_starttime,versions_endtime,versions_xid,versions_operation,ename
2* from tyger versions between timestamp to_timestamp(‘2014-03-14 14:41:46‘,‘yyyy-mm-dd hh24:mi:ss‘) and maxvalue order by 1
TYGER@ORCL>/
VERSIONS_STARTTIME VERSIONS_ENDTIME VERSIONS_XID V ENAME
---------------------- ---------------------- ---------------- - ----------
14-MAR-14 02.42.17 PM 14-MAR-14 02.42.26 PM 0600180025020000 U SMITH
14-MAR-14 02.42.26 PM 14-MAR-14 02.42.32 PM 01002C00F1010000 U SMITH
14-MAR-14 02.42.32 PM 080016000F020000 U SMITH
WARD
ALLEN
JONES
14-MAR-14 02.42.17 PM SMITH
7 rows selected.
实验三：闪回事务查询
flashback 的事务查询时通过查询flashback_transaction_query视图来实现的
通过查询该视图能够获得一些事务执行时的信息，甚至包括UNDO语句。
每个事务都有事务ID以及SCN关联关系
闪回事务处理查询是一中诊断工具，可以用来查看在事务处理级对数据库所做的更改。这样，可诊断数据库中的问题并对事务处理执行分析和审计。
可以使用FLASHBACK_TRANSACTION_QUERY视图来确定所有必要的SQL语句，这些语句可用来还原特定事务处理或特定时间段内所做的修改。
· 在数据库中，DDL操作只是对数据字典所做的一系列空间管理操作和更改。通过执行DDL对事务处理执行闪回事务处理查询时，会显示对数据字典所做的更改。
· 当闪回事务处理查询涉及到已从数据库中删除的表时，就不会反映表名称。而是使用对象编号。
· 如果闪回了执行事务处理的用户，则该事务处理的闪回事务处理查询只显示相应的用户ID，而不是用户名。
TYGER@ORCL>conn / as sysdba
Connected.
SYS@ORCL>
SYS@ORCL>
SYS@ORCL>select undo_sql from flashback_transaction_query where xid=‘080016000F020000‘;
UNDO_SQL
--------------------------------------------------------------------------------
update "TYGER"."TYGER" set "SAL" = ‘1057‘ where ROWID = ‘AAANQ3AAGAAAAYMAAA‘;
SYS@ORCL>grant select any transaction to tyger;
Grant succeeded.
SYS@ORCL>conn tyger/tyger
Connected.
TYGER@ORCL>select undo_sql from flashback_transaction_query where xid=‘080016000F020000‘;
UNDO_SQL
--------------------------------------------------------------------------------
update "TYGER"."TYGER" set "SAL" = ‘1057‘ where ROWID = ‘AAANQ3AAGAAAAYMAAA‘; //undo语句