Oracle OCP 19c 认证1Z0-083考试(第4题)

Posted 2021-07-09 itsaka

Which three are true about requirements for various FLASHBACK operations? (Choose three.)

• A. FLASHBACK transaction query requires undo to retrieve all versions of a row that existed between two points in time.
• B. FLASHBACK drop requires that the RECYCLEBIN parameter be set to ON.
• C. FLASHBACK version query requires that the RECYCLEBIN parameter be set to ON.
• D. FLASHBACK DATA ARCHIVE requires undo to store all versions of all rows of a table being tracked.
• E. FLASHBACK drop requires undo to retrieve all versions of a row that existed between two points in time.
• F. FLASHBACK version query requires undo to retrieve all versions of a row that existed between two points in time.

 

 

A B F

 

F is definitely right. Reference: https://oracle-base.com/articles/10g/flashback-version-query-10g "Flashback version query is based on UNDO. As a result, the amount of time you can flashback is dependent on how long undo information is retained, as specified by the UNDO_RETENTION parameter."

 

Oracle Flashback Query : retrieve data for a time in the past that you specify using the AS OF clause of the SELECT statement.

Oracle Flashback Version Query: retrieve metadata and historical data for a specific time interval. You can view all the rows of a table that ever existed during a given time interval. Metadata about the different versions of rows includes start and end time, type of change operation, and identity of the transaction that created the row version. You use the VERSIONS BETWEEN clause of the SELECT statement to create a Flashback Version Query.

Oracle Flashback Transaction Query : retrieve metadata and historical data for a given transaction, or for all transactions within a given time interval. You can also obtain the SQL code to undo the changes to particular rows affected by a transaction. You typically use Flashback Transaction Query in conjunction with a Flashback Version Query that provides the transaction IDs for the rows of interest. To perform a Flashback Transaction Query, you select from the FLASHBACK_TRANSACTION_QUERY view.

DBMS_FLASHBACK package : set the clock back to a time in the past, to examine data current at that time.