Explanation: Data structures such as B+-trees would not be in a consistent state, and neither logical redo nor logical undo operations can be performed on an inconsistent data structure. 6. An operation is said to be __________ if executing it several times in a row gives the same result as executing it once.
A. Idempotent
B. Changed
C. Repetitive
D. All of the above
Answer:A
Explanation: Data structures such as B+-trees would not be in a consistent state, and neither logical redo nor logical undo operations can be performed on an inconsistent data structure. 6. An operation is said to be __________ if executing it several times in a row gives the same result as executing it once.
A. Idempotent B. Changed C. Repetitive D. All of the above
Explanation:Operations such as inserting an entry into a B+-tree may not be idempotent, and the recovery algorithm must therefore make sure that an operation that has already been performed is not performed again. 7. Immediate database modification technique uses