In the world of database management it is crucial to ensure data integrity and reliability.

What is ACID?

ACID is a set of properties that guarantee reliable processing of database transactions. Let's break down each component:

Atomicity:

• Description: Ensures that a transaction is treated as a single, indivisible unit.
• Principle: All operations in a transaction either complete successfully or fail altogether.
• Example: In a bank transfer, both the withdrawal and deposit must succeed, or neither should occur.

Consistency:

• Description: Ensures that a transaction brings the database from one valid state to another.
• Principle: All data written to the database must be valid according to all defined rules.
• Example: If a table requires a unique ID, a transaction cannot leave the database with duplicate IDs.

Isolation:

• Description: Ensures that concurrent execution of transactions leaves the database in the same state as if the transactions were executed sequentially.
• Principle: Transactions cannot interfere with each other while in progress.
• Example: If two users are updating the same record, one user's changes should not be visible to the other until the transaction is complete.

Durability:

• Description: Ensures that once a transaction has been committed, it will remain committed even in the case of a system failure.
• Principle: Committed data is saved by the system in a way that even if there's a crash or power loss, the data will be available in its correct state when the system is restarted.
• Example: After a user receives a confirmation for a transaction, that data will be available even if the database crashes immediately after.

Importance of ACID

ACID properties are crucial for several reasons:

1. Data Integrity: They ensure that data remains accurate and consistent over time.
2. Reliability: They provide a guarantee that transactions will be processed as expected, even in the face of errors or system failures.
3. Concurrency Control: They allow multiple users to work with the same data simultaneously without conflicts.

ACID in Different Database Systems

While ACID properties are fundamental to relational databases, different types of databases may implement ACID differently:

• Relational Databases (e.g., MySQL, PostgreSQL): Fully support ACID properties.
• NoSQL Databases (e.g., MongoDB, Cassandra): May sacrifice some ACID properties for performance and scalability.
• NewSQL Databases (e.g., Google Spanner, CockroachDB): Aim to provide ACID guarantees with the scalability of NoSQL systems.