flashback
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1.flashback query闪回查询 (undo )
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select current_scn from v$database;


select * from t as of scn 2387032;






select systimestamp from dual;
select scn_to_timestamp(2387032) from dual;
select timestamp_to_scn('03-NOV-14 06.47.55.000000000 PM') from dual;


select * from t as of timestamp sysdate-5/1440;

SYSDATE-5/1440是啥意思，1440又是怎么来的？
首先60（分）×24=1440，这样就计算出一天拥有多少分钟，SYSDATE是系统函数，用来取得当前的系统时间（以天为单位），SYSDATE-5/1440，得出的就是距当前时间5分钟前的记录了。后面示例中需要计算之前的某个时段时，均是使用这一方法。


2.flashback table (undo)
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flashback table t to scn 2387032;


flashback table  t to timestamp to_timestamp('2009-1-4 22:21:11', 'yyyy-mm-
dd hh24:mi:ss');


ora_08189： cannot flashback the table because movemont is not enable;
解决：
select row_movement from dba_tables where table_name='T' and owner='HR';
alter table t enable row movement;


alter table t disable row movement;


3.flashback versions query (undo)
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--查询伪列
select versions_startscn,versions_endscn,versions_xid,versions_operation,versions_starttime,versions_endtime,id,name from t versions between scn minvalue and maxvalue oreder by versions_startscn;


4.flashback transaction query(undo)
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select * from flashback_transaction_query where where xid='...'




5.flashback drop (table)


show recyclebin;
select * from dba_recyclebin;
select * from dba_objects where object_name='BIN$BRCtqVHonmLgUAB/AQAXIQ==$0';


flashback table "BIN$BRCtqVHonmLgUAB/AQAXIQ==$0" to before drop;


闪回drop 前的表是，索引及触发器都能闪回，但名字是回收站的名字，需手工重命名；


alter index  "BIN$BRCtqVHonmLgUAB/AQAXIQ==$0" rename to idx_t1;


6.flashback database
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select flashback_on from v$database;


前提：
1.archivelog 模式
2.flash recovery area(flashback log);


alter database archivelog;
alter database flashback on;


select * from v$bgprocess where paddr<>'00';




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select * from v$flashback_database_stat;
select * from v$flashback_database_log;
select * from v$flashback_database_logfile;


mount 状态下


flashback database to scn 2387032;