Practice important DBMS Concurrency Control MCQ questions with answers and explanations. These questions cover key concepts like transactions, ACID properties, locking, isolation levels, and concurrency problems. Useful for IBPS IT Officer, GATE, and other competitive exams.
Difficulty: Easy to Medium
Total Questions: 12
Important DBMS Concurrency Control MCQ Questions
Q1. What is the main goal of concurrency control in DBMS?
A. Increase redundancy
B. Ensure consistency during concurrent transactions
C. Improve data storage
D. Reduce memory usage
View Answer & Explanation
Answer: B
Explanation: Concurrency control ensures that multiple transactions can execute safely without violating database consistency.
Q2. Which of the following is NOT a concurrency problem?
A. Lost Update
B. Dirty Read
C. Redundant Data
D. Phantom Read
View Answer & Explanation
Answer: C
Explanation: Lost update, dirty read, and phantom read are concurrency issues, whereas redundancy is a design issue.
Q3. What is a Dirty Read?
A. Reading committed data
B. Reading uncommitted data
C. Writing data twice
D. Deleting data accidentally
View Answer & Explanation
Answer: B
Explanation: A dirty read occurs when a transaction reads data that has not yet been committed by another transaction.
Q4. What is a Lost Update problem?
A. Data is deleted permanently
B. Two transactions overwrite each other’s updates
C. Data is duplicated
D. Data is encrypted
View Answer & Explanation
Answer: B
Explanation: Lost update occurs when two transactions update the same data and one update overwrites the other.
Q5. Which isolation level prevents dirty reads?
A. Read Uncommitted
B. Read Committed
C. Repeatable Read
D. Serializable
View Answer & Explanation
Answer: B
Explanation: Read Committed ensures that only committed data is read, preventing dirty reads.
Q6. Which isolation level provides the highest consistency?
A. Read Uncommitted
B. Read Committed
C. Repeatable Read
D. Serializable
View Answer & Explanation
Answer: D
Explanation: Serializable is the strictest isolation level, ensuring complete transaction isolation.
Q7. Two-Phase Locking (2PL) ensures:
A. Faster execution
B. Serializability
C. Data redundancy
D. Data compression
View Answer & Explanation
Answer: B
Explanation: 2PL guarantees conflict serializability by dividing execution into growing and shrinking phases.
Q8. In Two-Phase Locking, the growing phase involves:
A. Releasing locks
B. Acquiring locks only
C. Both acquiring and releasing locks
D. No locks used
View Answer & Explanation
Answer: B
Explanation: In the growing phase, transactions acquire locks and do not release any.
Q9. What is a Phantom Read?
A. Reading deleted data
B. Reading newly inserted rows during a transaction
C. Reading same data repeatedly
D. Reading null values
View Answer & Explanation
Answer: B
Explanation: Phantom reads occur when new rows are inserted by another transaction and appear during repeated queries.
Q10. Which of the following problems is prevented by Serializable isolation level?
A. Dirty Read
B. Lost Update
C. Phantom Read
D. All of the above
View Answer & Explanation
Answer: D
Explanation: Serializable prevents all concurrency anomalies including dirty reads, lost updates, and phantom reads.
Q11. Locking is primarily used to ensure:
A. Security
B. Consistency and isolation
C. Faster queries
D. Data backup
View Answer & Explanation
Answer: B
Explanation: Locks prevent conflicts between concurrent transactions, maintaining consistency and isolation.
Q12. Which of the following is NOT an ACID property?
A. Atomicity
B. Consistency
C. Isolation
D. Availability
View Answer & Explanation
Answer: D
Explanation: ACID stands for Atomicity, Consistency, Isolation, and Durability. Availability is not part of ACID.
Conclusion
These DBMS Concurrency Control MCQs help strengthen concepts like transactions, isolation levels, locking mechanisms, and concurrency anomalies. Regular practice improves understanding and performance in competitive exams.
For detailed theory, refer to DBMS Concurrency Control concepts .