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Oracle OCP 1Z0 053 Q43(Flashback Transaction(NOCASCADE_FORCE))

原创 Oracle 作者:abstractcyj 时间:2016-04-03 11:06:16 0 删除 编辑
43.View the following SQL statements:
Transaction T1 INSERT INTO hr.regions VALUES (5,'Pole');COMMIT;
Transaction T2 UPDATE hr.regions SET region_name='Poles' WHERE region_id = 5; COMMIT;
Transaction T3 UPDATE hr.regions SET region_name='North and South Poles' WHERE region_id = 5;
You want to back out transaction T2. Which option would you use?
A. It is possible, but transaction T3 also backs out.
B. It is possible with the NOCASCADE_FORCE option.
C. It is possible with the NONCONFLICT_ONLY option.
D. It is not possible because it has conflicts with transaction T3.
Answer: B

这里是FLASHBACK Transaction特性的知识点:
过程:DBMS_FLASHBACK.TRANSACTION_BACKOUT

NOCASCADE_FORCE - The user forcibly backs out the given transactions without considering the dependent transactions. The RDBMS executes the UNDO SQL for the given transactions in reverse order of their commit times. If no constraints break, and the result is satisfactory, the user can either COMMIT the changes or else ROLL BACK.

参考:https://docs.oracle.com/cd/B28359_01/appdev.111/b28419/d_flashb.htm

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曾从事java方向开发多年。近年已经转入数据库方向。主要擅长SQL优化,Oracle数据库问题诊断,Oracle备份与恢复等。服务于医药物流,医院等行业

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