Oracle Database Administration I — Question 97

Which three statements are true about sequences in a single instance Oracle database? (Choose three.)

Answer options

• A. Sequences can always have gaps.
• B. Two or more tables cannot have keys generated from the same sequence.
• C. A sequence's unallocated cached values are lost if the instance shuts down.
• D. A sequence can issue duplicate values.
• E. A sequence can only be dropped by a DBA.
• F. A sequence number that was allocated can be rolled back if a transaction fails.

Correct answer: A, C, D

Explanation

The correct answers A, C, and D highlight that sequences can inherently have gaps, unallocated values are lost on shutdown, and duplicate values can be produced. Options B and E are incorrect because multiple tables can use the same sequence for key generation, and sequences can also be dropped by users with the appropriate privileges, not just DBAs. Option F is wrong since allocated sequence numbers cannot be rolled back after they are issued.