ITPEC FE Morning April 2019 Question 29
ITPEC FE Morning April 2019 — Question 29 of 80
ACID — Atomicity — transaction is either fully completed or fully rolled back.
ACID properties:
- Atomicity — all or nothing; if any part fails, the entire transaction is rolled back
- Consistency — database moves from one valid state to another, all constraints satisfied
- Isolation — concurrent transactions do not interfere with each other
- Durability — once committed, changes survive system failures
Why not others:
- (b) Consistency — ensures valid state after transaction, not the all-or-nothing guarantee
- (c) Durability — ensures committed data persists after crashes
- (d) Isolation — ensures transactions don't see each other's intermediate states
Key rule: "Performed completely or canceled as if nothing happened" = Atomicity.
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