Explanation:Undo erases all the changes and redo makes the deleted changes. 10. If ___________ are not obtained in undo operation it will cause problem in undo-phase.
A. Higher-level lock
B. Lower-level lock
C. Read only lock
D. Read write
Answer:A
Explanation:Undo erases all the changes and redo makes the deleted changes. 10. If ___________ are not obtained in undo operation it will cause problem in undo-phase.
A. Higher-level lock B. Lower-level lock C. Read only lock D. Read write
Explanation: Operations acquire lower-level locks while they execute, but release them when they complete; the corresponding transaction must however retain a higher-level lock in a two-phase manner to prevent concurrent transactions from executing conflicting actions. Sanfoundry Global Education & Learning Series – Database Management System.