In the context of databases, ACID is an acronym that stands for Atomicity, Consistency, Isolation, and Durability. These are the four properties that ensure reliability and consistency in database transactions.
Atomicity: A transaction is atomic, meaning it is either completed in its entirety or not at all. This ensures that the database remains in a consistent state and prevents incomplete transactions from corrupting data.
Consistency: A transaction must maintain the consistency of the database, meaning that the data should be in a valid state both before and after the transaction.
Isolation: Transactions must be isolated from each other, so that they don't interfere with one another. This is necessary to prevent concurrent transactions from modifying the same data in unexpected ways.
Durability: Once a transaction is completed and committed, its changes must be durable and persistent, even in the event of system failure or power outage.