A transaction is delimited by statements (or function calls) of the form __________
Answer: A
Correct answer: Begin transaction and end transaction
A transaction is delimited by begin transaction and end transaction. The boundaries matter because they define what is atomic: everything between them succeeds together or is rolled back together. In practice the end is expressed as COMMIT or ROLLBACK.
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Which of the following are characteristics of a transaction?
Answer: D
Correct answer: All of the mentioned
The ACID properties are Atomicity (all or nothing), Consistency (the database moves from one valid state to another), Isolation (concurrent transactions do not see each other’s partial work) and Durability (a committed transaction survives a crash). All three listed are among them.
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Which of the following has “all-or-none” property?
Answer: A
Correct answer: Atomicity
Atomicity is the all-or-nothing property: a transaction either completes in full or has no effect at all. If it fails part way through, everything it has done is rolled back - which is what stops money being debited from one account and never credited to the other.
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The database system must take special actions to ensure that transactions operate properly without interference from concurrently executing database statements. This property is referred to as
Answer: C
Even though multiple transactions may execute concurrently, the system guarantees that, for every pair of transactions Ti and Tj, it appears to Ti that either Tj finished execution before Ti started or Tj started execution after Ti finished.
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The property of a transaction that survives system crashes is
Answer: B
Correct answer: Durability
Durability guarantees that once a transaction has committed, its changes survive any subsequent failure - power loss, crash, or restart. It is implemented by writing the changes to a log on stable storage before reporting the commit, so that recovery can replay them.
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__________ states that only valid data will be written to the database.
Answer: A
Correct answer: Consistency
Consistency requires that a transaction take the database from one valid state to another, preserving every integrity constraint - keys, referential integrity, and application rules such as an account balance never going negative. A transaction that would violate one is aborted.
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Transaction processing is associated with everything below except
Answer: C
Correct answer: Confirming an action or triggering a response
Transaction processing records business activity, maintains the data and produces reports from it. Confirming an action or triggering a response belongs to a real-time or decision support system rather than to transaction processing as such - which is concerned with capturing and storing what happened.
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The Oracle RDBMS uses the ____ statement to declare a new transaction start and its properties.
Answer: B
Correct answer: SET TRANSACTION
Oracle uses SET TRANSACTION to begin a transaction explicitly and set its properties - read-only or read-write, and the isolation level. Oracle needs no BEGIN: a transaction starts implicitly with the first DML statement, and SET TRANSACTION is used when the properties must be declared. BEGIN TRANSACTION is the SQL Server form.
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____ means that the data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.
Answer: D
Even though multiple transactions may execute concurrently, the system guarantees that, for every pair of transactions Ti and Tj, it appears to Ti that either Tj finished execution before Ti started or Tj started execution after Ti finished.
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Collections of operations that form a single logical unit of work are called __________
Answer: D
Correct answer: Transactions
A transaction is a set of operations that must be treated as one logical unit of work - the classic example being a transfer, where the debit and the credit are meaningless apart. Grouping them is what allows the ACID guarantees to be given at all.
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