ACIDturvallisuus

ACIDturvallisuus, or ACID safety, is a set of properties that guarantee reliable processing of database transactions. The acronym ACID stands for Atomicity, Consistency, Isolation, and Durability. These properties ensure that database transactions are processed reliably, even in the event of errors, power failures, or other system disruptions.

Atomicity ensures that each transaction is treated as a single "unit," which either completes entirely or fails completely. If any part of the transaction fails, the entire transaction is rolled back, and the database state is left unchanged.

Consistency ensures that a transaction brings the database from one valid state to another, maintaining database invariants. Any data written to the database must be valid according to any combination of rules, including cascades, constraints, and any combination thereof.

Isolation ensures that concurrently executing transactions remain unaware of each other. Intermediate states resulting from a transaction are invisible to other transactions. Isolation is achieved through concurrency control, which can be implemented using various methods such as locking or multi-version concurrency control.

Durability ensures that once a transaction has been committed, it will remain so, even in the event of a system failure. This is typically achieved through the use of transaction logs, which allow the database to recover to a consistent state after a failure.

ACID properties are crucial for maintaining data integrity and consistency in database systems. However, they can also lead to performance overhead, as they require additional processing to ensure reliability. In some cases, especially in high-performance or distributed systems, alternative approaches such as BASE (Basically Available, Soft state, Eventual consistency) may be used to achieve a balance between performance and reliability.