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Module 7 Final Quiz: Transactions & ACID Properties MCQs
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1
What does the Atomicity property of a transaction guarantee?
A.
That transactions execute in less than 1 millisecond
B.
All-or-nothing execution: either all operations of the transaction complete successfully, or the entire transaction is rolled back to leave the database unchanged
C.
That data is stored in atoms in silicon memory
D.
That only one user can access the table at a time
Explanation & Key
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2
What does Consistency guarantee in the ACID model?
A.
That the system runs at a consistent clock speed
B.
That a transaction transitions the database from one valid state satisfying all schema rules, integrity constraints, and cascades to another valid state
C.
That reading data twice returns the same value
D.
That disk writes never fail
Explanation & Key
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3
What does the Isolation property guarantee?
A.
The server is disconnected from the public internet
B.
Intermediate, uncommitted modifications made by one transaction remain invisible to all other concurrently executing transactions
C.
Each user has their own dedicated database instance
D.
Queries cannot access disk storage
Explanation & Key
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4
What does Durability guarantee in ACID?
A.
Hard drives will not physically break for 5 years
B.
Once a transaction successfully commits, its changes are permanently recorded in non-volatile storage and will survive even a sudden power loss or system crash
C.
Transactions cannot be aborted once started
D.
Data is backed up to tape drive every night
Explanation & Key
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5
What is Write-Ahead Logging (WAL) in database recovery?
A.
Writing user SQL scripts to GitHub before executing them
B.
The architectural rule that log records describing data modifications must be flushed to non-volatile disk storage BEFORE the corresponding modified database pages are written to disk
C.
Writing data to RAM before writing to CPU registers
D.
Writing queries in uppercase before lowercase
Explanation & Key
Correct Answer:
6
In the Transaction State Machine, when does a transaction transition from 'Partially Committed' to 'Committed'?
A.
Immediately after the user presses Enter on the keyboard
B.
After the final operation has executed AND the commit log record has been successfully flushed to non-volatile disk storage
C.
When the application process exits
D.
When the database reboots
Explanation & Key
Correct Answer:
7
What action does the DBMS recovery subsystem perform during ROLLBACK?
A.
Deletes all tables from the database
B.
Uses the Undo log records to reverse all modifications made by the aborted transaction, restoring affected rows to their pre-transaction values
C.
Restarts the computer operating system
D.
Sends an email alert to the system administrator
Explanation & Key
Correct Answer:
8
What is the purpose of Checkpointing in database recovery management?
A.
Taking screenshots of user dashboards
B.
Periodically flushing all dirty buffer pages to disk and writing a checkpoint record to the log, bounding how far back the recovery engine must scan during crash recovery
C.
Validating user passwords every 15 minutes
D.
Checking if hard drives have bad sectors
Explanation & Key
Correct Answer:
9
In the ARIES recovery algorithm, what are the three phases executed after a crash?
A.
Boot, Compile, Execute
B.
Analysis (identify active txns and dirty pages), Redo (replay history to crash state), and Undo (rollback uncommitted txns)
C.
Lock, Unlock, Terminate
D.
Select, Project, Join
Explanation & Key
Correct Answer:
10
What is a Compensating Log Record (CLR) in database recovery?
A.
A record paying the database administrator overtime
B.
A special log record written during the Undo phase to log the undoing of an action, preventing the recovery system from re-undoing it if a second crash occurs during recovery
C.
A log record that compresses data
D.
An index leaf node pointer
Explanation & Key
Correct Answer:
11
What is a SAVEPOINT in Transaction Control Language?
A.
An automatic cloud backup
B.
A marker within a transaction that allows selective partial rollback without aborting the entire transaction
C.
A permanent commit marker that cannot be undone
D.
A password protected directory
Explanation & Key
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