How does a transaction ensure data integrity and safety in a system?

A transaction ensures data integrity and safety through the properties of ACID:

• Atomicity — all operations within a transaction are completed fully or not at all. If something goes wrong, all changes are rolled back.
• Consistency — a transaction moves the system from one correct state to another, adhering to all constraints and rules.
• Isolation — concurrent transactions do not affect each other; changes made by one transaction are not visible to others until it is completed.
• Durability — after a transaction successfully completes, changes are saved and not lost even in case of failures.

For example, when transferring money between accounts, a transaction guarantees that the debit from one account and the credit to another happen together or not at all, preventing partial updates and errors.