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 files
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