Free Transactions and concurrency lessonsTransactions and concurrency · Stage 0 · All or nothing · Step 1
Transactions and ACID
See what goes wrong when a multi-step change is interrupted, and the four guarantees a transaction gives. About 13 minutes.
A transaction has run two of its three updates when the server loses power. After restart, what does atomicity guarantee?
- ANone of the three updates is visible: the whole transaction is rolled back
- BThe two completed updates remain, and the third is retried automatically
- CAll three updates are completed after restart
Show the answer
None of the three updates is visible: the whole transaction is rolled back. It never committed, so the database undoes its partial work.
4 questions on this idea
Short questions that apply the idea to new cases: trace it, work out a number, put steps in order. A wrong answer explains itself.
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