ACID & transaction correctness
Understand the concept
ACID describes four properties used to reason about reliable transactions: atomicity, consistency, isolation and durability. Together they address partial changes, preserved rules, concurrent work and persistence after commit. They do not automatically supply correct business rules or the strongest isolation level.
Important ideas
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Atomicity: all transaction changes succeed or none do.
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Consistency: declared rules remain valid; isolation: concurrent work has defined visibility.
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Durability: committed changes survive failures under the database's durability settings.
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For a transfer, debit and credit should commit together, while a constraint or application rule prevents an invalid balance.
Can you explain it without the notes?
What does ACID mean?
Use your own words. Explain an example and one limitation before checking the explanation.
Check your explanation
ACID describes four properties used to reason about reliable transactions: atomicity, consistency, isolation and durability. Together they address partial changes, preserved rules, concurrent work and persistence after commit. They do not automatically supply correct business rules or the strongest isolation level.
Turn this concept into a clear answer.
- Database consistency in ACID means preserving defined invariants; it is not the same definition as consistency in CAP.
Adapted from 05_SQL_POSTGRESQL.md · “What does ACID mean?”. Examples are study fragments; framework behavior can depend on your version.