The ACID Paradigm
The properties of a transaction are atomicity, consistency, isolation, and durability, forming the mnemonic acronym ACID. We briefly define these properties as follows:
- Atomicity (A): Guarantees that a transaction is treated as a single “unit” of operation. All operations within the transaction succeed, or the entire transaction is rolled back. This prevents partial updates to the database, ensuring data integrity.
- Consistency (C): Ensures that a transaction transforms the database from one valid state to another. All rules, constraints, and integrity conditions must be met before and after the transaction. This maintains the reliability of the database.
- Isolation (I): Ensures that concurrent execution of transactions results in a state that would be obtained if transactions were executed serially in some order. Each transaction should be isolated from other transactions, preventing them from interfering with each other’s operations or seeing intermediate results.
- Durability (D): Once a transaction has been committed, it will remain so, even in the event of power loss, crashes, or errors. Durability is typically achieved by writing completed transactions to non-volatile storage.