DatabasesLesson 1 of 4 in the course Transactions and concurrency

ACID Transactions: Guarantees, Recovery, and Distributed Trade-offs

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

ACID describes four properties that help database transactions keep data valid and dependable, even when errors or failures occur. This lesson introduces the transaction model and focuses on atomicity and consistency.

A transaction is a logical unit of database work. It may contain several operations, but the database treats them as one overall task. For example, transferring money between accounts involves both debiting one account and crediting another.

All flashcards

What does ACID stand for?
Atomicity, consistency, isolation, and durability—the properties used to describe reliable database transactions.
What does consistency require of a committed transaction?
It must preserve applicable database rules and invariants, leaving the database in a valid state.
What is write-ahead logging?
A recovery approach that records changes in a persistent log before applying them to the database.
How does multiversion concurrency control (MVCC) help readers and writers?
It maintains multiple data versions so readers can use an earlier version while writers create a newer one.
What is the role of two-phase commit?
It coordinates distributed participants so a transaction is committed as a whole or not committed.

Quiz questions

  1. Which property requires concurrent transactions to produce results equivalent to an acceptable sequential execution?Answer: Isolation
  2. A database confirms a transaction as committed, but a power failure erases its changes. Which property was violated?Answer: Durability
  3. Which statement about snapshot isolation is accurate?Answer: It provides a consistent snapshot but is not necessarily serializable.
  4. In two-phase commit, what happens if every participant reports that it is prepared?Answer: The coordinator proceeds to formalize the commit.
  5. Which description best captures the general priority of BASE-style systems?Answer: They emphasize availability and can tolerate temporary inconsistency before data converges.

Based on the Wikipedia article ACID, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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