Why are transaction isolation levels important in database management systems?

Transaction isolation levels are important for managing concurrent access to data in a database and ensuring data integrity. They define how and when changes made by one transaction become visible to other transactions.

Main reasons for their importance:

• Preventing anomalies: isolation levels help avoid issues such as dirty reads, non-repeatable reads, and phantom reads.
• Balancing performance and integrity: higher isolation levels provide greater integrity but reduce concurrency and performance.
• Guaranteeing data consistency: transactions operate as atomic operations, and isolation levels help ensure that data is not corrupted when multiple users work simultaneously.

For example, the "Read Committed" level prevents dirty reads, while "Serializable" provides full transaction isolation but may lead to locking and reduced performance.