Oracle Linux 8 System Administration — Question 2

Which three statements are true about UNDO and REDO? (Choose three.)

Answer options

• A. Both REDO and UNDO can be multiplexed.
• B. UNDO is used for read consistency.
• C. REDO is used for ROLLBACK.
• D. REDO is used for instance recovery.
• E. REDO is used for read consistency.
• F. UNDO is used for some flashback operations.

Correct answer: A, B, D

Explanation

The correct answers are A, B, and D. A is true because both UNDO and REDO can be multiplexed to enhance reliability. B is correct as UNDO guarantees read consistency by allowing transactions to access previous versions of data. D is accurate since REDO is essential for instance recovery to restore the database to a consistent state after a failure. Options C and E are incorrect; REDO is not used for ROLLBACK, and it does not provide read consistency.