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
从图中可以看出 retention guarantee 为 yes，Undo Retention 为 60，所以保留时间最少为 1 小时，有因为没有超过1 小时的提交的事务，所以不会覆盖，只会报错。
原文：http://www.cnblogs.com/Babylon/p/7986874.html