Database Systems, unit: Transactions and Concurrency Control. Core concepts, terminology, and worked-example cues a college student meets for this unit, building on prior units without repeating them. Front: a term, concept, or short problem cue. Back: the definition, explanation, or answer.
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- What is a database transaction?
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A sequence of operations performed as a single logical unit of work- What does ACID stand for?
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Atomicity, Consistency, Isolation, and Durability- What is atomicity, in ACID?
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A transaction either fully completes or has no effect at all- What is consistency, in ACID?
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A transaction brings the database from one valid state to another- What is isolation, in ACID?
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Concurrent transactions do not interfere with each other's intermediate states- What is durability, in ACID?
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Once a transaction commits, its changes persist even after a system failure- What is a commit, in a transaction?
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An operation that permanently saves all changes made during a transaction- What is a rollback, in a transaction?
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An operation that undoes all changes made during an incomplete or failed transaction- What is concurrency control?
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Techniques ensuring correct results when multiple transactions run simultaneously- What is a race condition, in database terms?
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An error caused by unsynchronized concurrent access to shared data- What is a lock, in concurrency control?
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A mechanism that restricts access to data to prevent conflicting concurrent operations- What is a deadlock, in database transactions?
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A situation where two or more transactions wait indefinitely for each other's locks- What is a dirty read?
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Reading uncommitted data from another transaction that may later be rolled back- What is a non-repeatable read?
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Reading the same row twice within a transaction and getting different values- What is a phantom read?
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A transaction reads a set of rows twice and finds new rows added by another transaction
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