Which two statements are true regarding undo data records? (Choose two.)

Question

Options

• AThey are required to support Flashback features.
• BI hey are not required if Flashback features are enabled.
• CThey are retained until the session making the changes ends.
• DUndo records contain copies of data as it appears after a change is made.
• EUndo records contain copies of data as it appears before a change is made.

• A
  75% (21)
• B
  7% (2)
• C
  4% (1)
• D
  14% (4)

Explanation

Oracle Database creates and manages information that is used to roll back, or undo, changes to the database. Such information consists of records of the actions of transactions, primarily before they are committed. These records are collectively referred to as undo. Undo records are used to: - Roll back transactions when a ROLLBACK statement is issued - Recover the database - Provide read consistency - Analyze data as of an earlier point in time by using Oracle Flashback - Recover from logical corruptions using Oracle Flashback features When a ROLLBACK statement is issued, undo records are used to undo changes that were made to the database by the uncommitted transaction. During database recovery, undo records are used to undo any uncommitted changes applied from the redo log to the data files. Undo records provide read consistency by maintaining the before image of the data for users who are accessing the data at the same time that another user is changing it.

No community discussion yet for this question.