单项选择题
A. Flashback Versions Query is used to make changes to multiple versions of data that existed between two points in time.
B. Flashback Versions Query is used to view all version changes on rows that existed between the time the query was executed and a point in time in the past.
C. Flashback Versions Query is used to view version changes and the SQL to undo those changes on rows that existed between two points in time.
D. Flashback Versions Query is used to view all version changes on rows that existed between two points in time.
多项选择题 Users notify you that their application is failing every time they try to add new records. Because of poor application design， the actual ORA error message is unavailable. What might be the problem？（）
多项选择题 InordertoperformFlashbackTransactionQueryoperations，whichofthesestepsarerequired？（）
单项选择题 AUM has been retaining about 15 minutes worth of undo. You want to double the retentionperiod， but not at the expense of new transactions failing. You decide to alter the system to set the parameter UNDO_RETENTION=18000. However， AUM still retains only about 15 minutes worth of undo. What is the problem？ （）