1.閃回事務處理功能的前提
sql> show user;
user is "sys"
sql> alter database add supplemental log data;
database altered.
sql> alter database add supplemental log data(primary key) columns;
database altered.
sql> grant execute on dbms_flashback to scott;
grant succeeded.
sql> grant select any transaction to scott;
grant succeeded.
2.建立一張實驗表
sql> create table t (id number,name varchar2(10));
table created.
第乙個事務，插入兩行，提交
sql> insert into t values(1,'a');
1 row created.
sql> insert into t values(2,'b');
1 row created.
sql> commit;
commit complete.
第二事務，插入5行，提交
sql> insert into t values(3,'c');
1 row created.
sql> insert into t values(3,'c');
1 row created.
sql> insert into t values(3,'c');
1 row created.
sql> insert into t values(3,'c');
1 row created.
sql> insert into t values(3,'c');
1 row created.
sql> commit;
commit complete.
執行乙個閃回版本查詢
sql>select versions_starttime,versions_endtime,versions_startscn,
versions_endscn,versions_xid,versions_operation from scott.t1
versions between scn minvalue and maxvalue order by 1;
versions_starttime versions_endtime versions_startscn versions_endscn versions_xid v
30-may-16 02.44.39 pm 30-may-16 02.55.33 pm 1040502 1042027 02000500b2020000 i
30-may-16 02.44.39 pm 30-may-16 02.55.33 pm 1040502 1042027 02000500b2020000 i
30-may-16 02.45.15 pm 1040522 01001f00fc010000 i
30-may-16 02.45.15 pm 1040522 01001f00fc010000 i
30-may-16 02.45.15 pm 1040522 01001f00fc010000 i
30-may-16 02.45.15 pm 1040522 01001f00fc010000 i
30-may-16 02.45.15 pm 1040522 01001f00fc010000 i
30-may-16 02.55.33 pm 1042027 01002100fc010000 d
30-may-16 02.55.33 pm 1042027 01002100fc010000 d
3.執行閃回事務查詢
閃回事務查詢，可以看到，一共兩個事務，乙個事務包含兩條dml，乙個事務包含五條dml
通過undo_sql欄位給出反sql
我們可以手動的取消某乙個事務
但是，當事務比較複雜，事務中包含dml較多的情況下
手動去執行閃回事務處理，將變得困難，且容易出錯
資料庫提供了dbms_flashback.transaction_backout函式
幫助我們自動的，去執行同乙個事務下，所有反sql
能夠保障事務的完整性
sql> select xid,operation,undo_sql
2 from flashback_transaction_query
3 where table_name='t';
xid operation undo_sql
01000200ed010000 insert delete from "scott"."t" where rowid = 'aaaso5aaeaa
aaiuaab';
01000200ed010000 insert delete from "scott"."t" where rowid = 'aaaso5aaeaa
aaiuaaa';
06000b00af020000 insert delete from "scott"."t" where rowid = 'aaaso5aaeaa
aaiuaag';
06000b00af020000 insert delete from "scott"."t" where rowid = 'aaaso5aaeaa
aaiuaaf';
06000b00af020000 insert delete from "scott"."t" where rowid = 'aaaso5aaeaa
aaiuaae';
06000b00af020000 insert delete from "scott"."t" where rowid = 'aaaso5aaeaa
aaiuaad';
06000b00af020000 insert delete from "scott"."t" where rowid = 'aaaso5aaeaa
aaiuaac';
7 rows selected.
4.執行閃回事務處理
閃回事務處理需要sys使用者去執行
sql> show user;
user is "sys"
sql> declare
2 v_xid sys.xid_array;
3 begin
4 v_xid := sys.xid_array('01000200ed010000');
5 dbms_flashback.transaction_backout(1,v_xid);
6 end;
7 /pl/sql procedure successfully completed.
在當前會話，查詢閃回之後的結果，因為此時該事務未提交，所以別的會話看不到閃回後的結果
在確認，閃回達到預期之後，提交
sql> select * from scott.t;
id name
3 c3 c
3 c3 c
3 csql> commit;
commit complete.
回到scott進行確認
sql> select * from t;
id name
3 c3 c
3 c3 c
3 c
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