The ACID properties are essential in database systems to ensure reliable transactions. ACID stands for Atomicity, Consistency, Isolation, and Durability.

1. Atomicity: This ensures that all parts of a transaction are completed successfully or none are. For instance, in a bank transfer, both the withdrawal from account A and deposit into account B must happen, or neither does. If a failure occurs, the transaction is rolled back.
2. Consistency: This property ensures that a transaction brings the database from one valid state to another, maintaining database rules. For example, in a banking system, the total balance should remain consistent before and after transferring Rs100.
3. Isolation: Transactions should operate independently without interference. For instance, if two transactions try to update the same account simultaneously, isolation ensures one completes before the other starts, preventing conflicts.
4. Durability: Once a transaction is committed, it remains so, even in the case of a system crash. For example, after completing a transfer, the system ensures the updated balances are saved permanently, even if the power goes out immediately afterward.

Example: Consider transferring Rs100 from A’s account to B’s account.

• Atomicity: Ensure both accounts are updated, or neither is.
• Consistency: Ensure A’s account decreases by Rs100, and B’s increases by Rs100, maintaining the total.
• Isolation: Ensure no other transaction can modify these accounts during the transfer.
• Durability: Once the transfer completes, the changes remain even if the database crashes.