28. View the Exhibit and examine the undo tablespace attributes.
Your database instance is experiencing a large volume of transactions from non-DBA users in the last one
hour. The undo tablespace UNDOTBS1 is full with transactions and no transaction was committed more
than one hour ago. The database has two more undo tablespaces.
What happens to the new DML operations in this scenario?
A.The DML commands will fail.
B.The undo data generated by the DML is stored in one of the two other undo tablespaces.
C.The undo data generated by the DML will overwrite the extents that contain committed undo data.
D.The undo data generated by the DML is stored in the SYSTEM undo segment of the SYSTEM
tablespace.
Answer: A
答案解析：
默认还原行为是覆盖已提交、但尚未过期的事务处理的还原信息，而不是让活动事务处理因缺少还原空间而失败。
保证保留时间会改变此行为。有了保留时间保证，即使会导致事务处理失败，仍然会强制执行还原保留时间设置。
此题，设置了undo retention的时间为60分钟。
retention guarantee 设置为yes
并且auto_extensible设置为no
以上的设置，在undo表空间没有自动扩展，并且undo表空间已经满了，但是设置了retention guarantee即，保证保留时间为60分钟，新的事务不能覆盖旧的，所以后来的事务会失败。