Please keep at least one language enabled. || కనీసం ఒక భాషను ఎంచుకోండి.
Question 1
ప్రశ్న 1
Which statement best defines a database transaction?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• A transaction is a logical unit of work containing one or more database operations.
• The operations belonging to a transaction are managed together so that the transaction can either complete successfully or be rolled back when necessary.
• Transactions are fundamental to maintaining reliable database processing.
• The operations belonging to a transaction are managed together so that the transaction can either complete successfully or be rolled back when necessary.
• Transactions are fundamental to maintaining reliable database processing.
వివరణ:
Question 2
ప్రశ్న 2
What does the acronym ACID stand for in database transaction processing?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• ACID stands for Atomicity, Consistency, Isolation and Durability.
• These properties describe important requirements for reliable transaction processing.
• Each property addresses a different aspect of correct transaction execution and recovery.
• These properties describe important requirements for reliable transaction processing.
• Each property addresses a different aspect of correct transaction execution and recovery.
వివరణ:
Question 3
ప్రశ్న 3
A transaction transfers ₹5,000 from Account A to Account B. Account A is debited successfully, but a failure occurs before Account B can be credited. Which ACID property requires that the incomplete debit must not remain as the final transaction result?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• Atomicity requires a transaction to behave as an all-or-nothing unit.
• If every required operation of the transfer cannot be completed, the effects of the incomplete transaction must be undone.
• This prevents a partial transfer in which money is removed from one account without being added to the other.
• If every required operation of the transfer cannot be completed, the effects of the incomplete transaction must be undone.
• This prevents a partial transfer in which money is removed from one account without being added to the other.
వివరణ:
Question 4
ప్రశ్న 4
Which ACID property requires a correctly designed transaction to take a database from one valid state to another valid state while preserving defined integrity rules?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• Consistency means that a transaction preserves the database's defined integrity requirements.
• Assuming the database begins in a consistent state and the transaction is valid, successful completion should leave it in another consistent state.
• Atomicity concerns all-or-nothing execution, while durability concerns persistence after commit.
• Assuming the database begins in a consistent state and the transaction is valid, successful completion should leave it in another consistent state.
• Atomicity concerns all-or-nothing execution, while durability concerns persistence after commit.
వివరణ:
Question 5
ప్రశ్న 5
Two transactions execute concurrently. Which ACID property is primarily concerned with preventing one transaction from improperly observing another transaction's intermediate, unfinished changes?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• Isolation separates the effects of concurrently executing transactions so that unfinished intermediate work is not improperly exposed to other transactions.
• Conceptually, properly isolated concurrent transactions behave as though their effects were suitably serialized.
• Isolation is therefore especially important in multi-user database processing.
• Conceptually, properly isolated concurrent transactions behave as though their effects were suitably serialized.
• Isolation is therefore especially important in multi-user database processing.
వివరణ:
Question 6
ప్రశ్న 6
A transaction is successfully committed. Immediately afterward, the computer loses power. Which ACID property requires the committed changes to survive the failure?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• Durability requires the effects of a successfully committed transaction to persist.
• Once successful completion has been confirmed, subsequent system failure should not normally erase the committed database changes.
• Durability therefore concerns persistence after successful commit.
• Once successful completion has been confirmed, subsequent system failure should not normally erase the committed database changes.
• Durability therefore concerns persistence after successful commit.
వివరణ:
Question 7
ప్రశ్న 7
What is the primary effect of COMMIT at the successful completion of a database transaction?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• COMMIT marks the successful completion of a transaction.
• Database modifications performed by that transaction become permanent according to the DBMS's transaction mechanism.
• COMMIT is therefore fundamentally different from ROLLBACK, which reverses transaction changes.
• Database modifications performed by that transaction become permanent according to the DBMS's transaction mechanism.
• COMMIT is therefore fundamentally different from ROLLBACK, which reverses transaction changes.
వివరణ:
Question 8
ప్రశ్న 8
A transaction has modified several records but an error is detected before the transaction is committed. Which transaction-control operation is used to undo the uncommitted work?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• ROLLBACK reverses transaction modifications that have not been successfully committed, according to the specified rollback scope.
• It is used when a transaction must be cancelled because of an error or other condition.
• COMMIT would instead accept the transaction's completed changes.
• It is used when a transaction must be cancelled because of an error or other condition.
• COMMIT would instead accept the transaction's completed changes.
వివరణ:
Question 9
ప్రశ్న 9
What is the principal purpose of a SAVEPOINT within a database transaction?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• A savepoint marks an intermediate point inside a transaction.
• A rollback to that savepoint can undo subsequent work without necessarily cancelling all earlier work in the transaction.
• SAVEPOINT therefore provides finer control than rolling back the entire transaction.
• A rollback to that savepoint can undo subsequent work without necessarily cancelling all earlier work in the transaction.
• SAVEPOINT therefore provides finer control than rolling back the entire transaction.
వివరణ:
Question 10
ప్రశ్న 10
A transaction performs two operations: (1) debit ₹1,000 from Account X and (2) credit ₹1,000 to Account Y. The debit succeeds, but the credit operation fails before COMMIT. Which outcome best satisfies atomic transaction processing?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• The debit and credit are parts of one logical transfer transaction.
• Atomicity requires that the transfer be completed as a whole or that its incomplete effects be undone.
• Leaving only the debit would produce a partial transaction result and violate atomicity.
• Atomicity requires that the transfer be completed as a whole or that its incomplete effects be undone.
• Leaving only the debit would produce a partial transaction result and violate atomicity.
వివరణ:
Question 11
ప్రశ్న 11
In the common textbook transaction-state model, what is the initial state of a transaction while its read, write or other database operations are still being executed?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• A transaction enters the Active state when its execution begins.
• It remains active while its normal database operations are being performed.
• Successful execution of its final statement can move it toward the partially committed state.
• It remains active while its normal database operations are being performed.
• Successful execution of its final statement can move it toward the partially committed state.
వివరణ:
Question 12
ప్రశ్న 12
In the common transaction-state model, a transaction has successfully executed its final statement, but successful commitment has not yet been fully established. Which state is this?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• The Partially committed state occurs after the final transaction statement has executed but before the transaction is guaranteed to be successfully committed.
• A failure can still prevent final commitment at this stage.
• Once successful completion is established, the transaction moves to the Committed state.
• A failure can still prevent final commitment at this stage.
• Once successful completion is established, the transaction moves to the Committed state.
వివరణ:
Question 13
ప్రశ్న 13
In the common transaction-state model, a transaction is executing when a serious error occurs and normal execution can no longer proceed. Which state does the transaction enter?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• A transaction enters the Failed state when the system determines that normal execution can no longer continue.
• Causes can include transaction errors, system failures or other conditions preventing successful completion.
• The failed transaction must then have its incomplete effects handled, normally through rollback.
• Causes can include transaction errors, system failures or other conditions preventing successful completion.
• The failed transaction must then have its incomplete effects handled, normally through rollback.
వివరణ:
Question 14
ప్రశ్న 14
In the common transaction-state model, what is the state of a transaction after its effects have been rolled back and the database has been restored from that failed transaction's incomplete work?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• An Aborted transaction is one whose incomplete effects have been undone through rollback.
• The database is restored so that the failed transaction does not leave partial changes behind.
• Depending on the cause of failure and the system, an aborted transaction may later be restarted or terminated.
• The database is restored so that the failed transaction does not leave partial changes behind.
• Depending on the cause of failure and the system, an aborted transaction may later be restarted or terminated.
వివరణ:
Question 15
ప్రశ్న 15
In the common transaction-state model, which state indicates that a transaction has completed successfully and its effects have been accepted as permanent?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• The Committed state represents successful transaction completion.
• At this point, the transaction's effects have been accepted as permanent database changes.
• A failed or aborted transaction, in contrast, does not retain its incomplete effects.
• At this point, the transaction's effects have been accepted as permanent database changes.
• A failed or aborted transaction, in contrast, does not retain its incomplete effects.
వివరణ:
Question 16
ప్రశ్న 16
Which sequence correctly represents the normal successful path of a transaction in the common transaction-state model?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• A transaction normally begins in the Active state while its operations execute.
• After its final operation has executed, it can enter the Partially committed state.
• Once successful commitment is established, it enters the Committed state.
• After its final operation has executed, it can enter the Partially committed state.
• Once successful commitment is established, it enters the Committed state.
వివరణ:
Question 17
ప్రశ్న 17
Which sequence correctly represents the basic structure of an explicit database transaction?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• An explicit transaction begins with a transaction-start operation such as BEGIN TRANSACTION.
• Database operations are then executed as part of that transaction.
• The transaction is finally completed successfully with COMMIT or cancelled with ROLLBACK.
• Database operations are then executed as part of that transaction.
• The transaction is finally completed successfully with COMMIT or cancelled with ROLLBACK.
వివరణ:
Question 18
ప్రశ్న 18
Assertion (A): A SAVEPOINT can allow only part of an ongoing transaction to be undone.
Reason (R): Rolling back to a savepoint can discard changes made after that savepoint while preserving earlier transaction work for possible later commit.
Choose the correct answer.
Reason (R): Rolling back to a savepoint can discard changes made after that savepoint while preserving earlier transaction work for possible later commit.
Choose the correct answer.
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• Savepoints provide intermediate rollback points within an ongoing transaction.
• Rolling back to a savepoint can undo later operations without necessarily undoing everything performed before the savepoint.
• Both statements are therefore true, and the Reason correctly explains the Assertion.
• Rolling back to a savepoint can undo later operations without necessarily undoing everything performed before the savepoint.
• Both statements are therefore true, and the Reason correctly explains the Assertion.
వివరణ:
Question 19
ప్రశ్న 19
Match List I with List II:
List I
(a) Atomicity
(b) Consistency
(c) Isolation
(d) Durability
List II
1. Committed effects persist despite subsequent failures
2. Transaction preserves defined database validity rules
3. Transaction executes as an all-or-nothing logical unit
4. Concurrent transactions are protected from improper exposure to one another's intermediate work
Choose the correct matching code.
List I
(a) Atomicity
(b) Consistency
(c) Isolation
(d) Durability
List II
1. Committed effects persist despite subsequent failures
2. Transaction preserves defined database validity rules
3. Transaction executes as an all-or-nothing logical unit
4. Concurrent transactions are protected from improper exposure to one another's intermediate work
Choose the correct matching code.
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• Atomicity corresponds to all-or-nothing execution, giving (a)-3.
• Consistency concerns preserving defined database validity, giving (b)-2.
• Isolation concerns concurrent transactions, while Durability preserves committed effects, giving (c)-4 and (d)-1.
• Consistency concerns preserving defined database validity, giving (b)-2.
• Isolation concerns concurrent transactions, while Durability preserves committed effects, giving (c)-4 and (d)-1.
వివరణ:
Question 20
ప్రశ్న 20
A transaction updates Stock_A and Stock_B as part of one inventory adjustment. Stock_A is changed successfully, but an integrity error occurs before Stock_B can be updated and before COMMIT. What is the most appropriate transaction outcome?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
• Both updates belong to the same stated transaction and therefore form one logical unit of work.
• Because the transaction cannot complete successfully, its incomplete modifications should be rolled back rather than partially committed.
• This behaviour directly supports transaction atomicity and protects database consistency.
• Because the transaction cannot complete successfully, its incomplete modifications should be rolled back rather than partially committed.
• This behaviour directly supports transaction atomicity and protects database consistency.
వివరణ:
Answer Key సమాధానాల పట్టిక
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Question 1 ప్రశ్న 1Answer: B. A logical unit of database work consisting of one or more operations that are treated as a single unit సమాధానం: B.
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Question 2 ప్రశ్న 2Answer: D. Atomicity, Consistency, Isolation, Durability సమాధానం: D.
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Question 3 ప్రశ్న 3Answer: A. Atomicity సమాధానం: A.
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Question 4 ప్రశ్న 4Answer: C. Consistency సమాధానం: C.
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Question 5 ప్రశ్న 5Answer: A. Isolation సమాధానం: A.
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Question 6 ప్రశ్న 6Answer: C. Durability సమాధానం: C.
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Question 7 ప్రశ్న 7Answer: D. It successfully ends the transaction and makes its completed database changes permanent. సమాధానం: D.
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Question 8 ప్రశ్న 8Answer: B. ROLLBACK సమాధానం: B.
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Question 9 ప్రశ్న 9Answer: C. To mark a point within the transaction to which a partial rollback can later be performed సమాధానం: C.
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Question 10 ప్రశ్న 10Answer: B. Undo the transaction's debit so that the incomplete transfer does not remain. సమాధానం: B.
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Question 11 ప్రశ్న 11Answer: A. Active సమాధానం: A.
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Question 12 ప్రశ్న 12Answer: D. Partially committed సమాధానం: D.
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Question 13 ప్రశ్న 13Answer: D. Failed సమాధానం: D.
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Question 14 ప్రశ్న 14Answer: A. Aborted సమాధానం: A.
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Question 15 ప్రశ్న 15Answer: B. Committed సమాధానం: B.
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Question 16 ప్రశ్న 16Answer: C. Active → Partially committed → Committed సమాధానం: C.
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Question 17 ప్రశ్న 17Answer: B. BEGIN TRANSACTION → perform database operations → COMMIT or ROLLBACK సమాధానం: B.
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Question 18 ప్రశ్న 18Answer: D. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion. సమాధానం: D.
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Question 19 ప్రశ్న 19Answer: C. (a)-3, (b)-2, (c)-4, (d)-1 సమాధానం: C.
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Question 20 ప్రశ్న 20Answer: A. Roll back the transaction so that its incomplete Stock_A modification does not remain as a partial result. సమాధానం: A.