NSCT – Concurrency Control MCQs 20 min Score: 0 Attempted: 0/20 Subscribe 1. . Concurrency control in DBMS is used to: (A) Compress tables (B) Ensure correct execution of transactions when multiple users access the database simultaneously (C) Encrypt data (D) Backup filesShow All Answers 2. . The main goal of concurrency control is: (A) Maintain database consistency, isolation, and integrity (B) Compress tables (C) Encrypt data (D) Delete old records 3. . Serializability is: (A) Ensuring that the result of concurrent transactions is the same as if executed sequentially (B) Compressing tables (C) Encrypting tables (D) Deleting old data 4. . A schedule is: (A) An encrypted file (B) A compressed table (C) The order in which operations of transactions are executed (D) A backup log 5. . Conflict occurs when: (A) Data is encrypted (B) Tables are compressed (C) Two transactions access the same data and at least one writes it (D) Files are backed up 6. . A conflict-serializable schedule is: (A) A schedule that encrypts tables (B) A schedule that compresses tables (C) A schedule that can be transformed into a serial schedule by swapping non-conflicting operations (D) A schedule that deletes data 7. . Lost update problem occurs when: (A) Data is encrypted (B) Data is deleted automatically (C) Tables are compressed (D) Two transactions update the same data simultaneously, causing one update to be lost 8. . Dirty read occurs when: (A) Data is compressed (B) A transaction reads uncommitted changes of another transaction (C) Tables are encrypted (D) Old records are deleted 9. . Non-repeatable read occurs when: (A) Old data is deleted (B) Data is compressed (C) Tables are encrypted (D) A transaction reads the same data twice and gets different values due to other transactions 10. . Phantom problem occurs when: (A) Tables are encrypted (B) Data is compressed (C) A transaction reads a set of rows, and another transaction inserts/deletes rows in that set (D) Old records are deleted 11. . Two-phase locking (2PL) ensures: (A) Serializability by acquiring locks before access and releasing after execution (B) Compressing tables (C) Encrypting tables (D) Deleting old records 12. . Strict two-phase locking (Strict 2PL) requires: (A) All exclusive locks are released only after the transaction commits (B) Locks are released immediately (C) Tables are compressed (D) Data is encrypted 13. . Deadlock occurs when: (A) Data is encrypted (B) Data is deleted (C) Tables are compressed (D) Two or more transactions wait indefinitely for resources held by each other 14. . To prevent deadlock, one can use: (A) Timeout, Wait-Die, or Wound-Wait schemes (B) Compression (C) Encryption (D) Backup logs 15. . Timestamp-based protocols assign: (A) Encryption keys (B) Compression codes (C) A unique timestamp to each transaction to order operations (D) Backup schedules 16. . Multiversion concurrency control (MVCC) allows: (A) Multiple versions of data to exist to reduce conflicts (B) Tables to compress automatically (C) Data to encrypt automatically (D) Old records to delete automatically 17. . Read-write conflict occurs when: (A) One transaction reads data while another writes it simultaneously (B) Both transactions delete data (C) Both transactions compress tables (D) Data is encrypted 18. . Write-write conflict occurs when: (A) Data is compressed (B) Transactions read data only (C) Two transactions write the same data simultaneously (D) Data is encrypted 19. . Optimistic concurrency control assumes: (A) Conflicts happen frequently (B) Conflicts are rare and checks are made at commit time (C) Data is compressed (D) Data is encrypted 20. . The main purpose of Concurrency Control is to: (A) Encrypt data (B) Compress tables (C) Ensure correctness, consistency, and isolation of concurrent transactions (D) Delete old records
