Final answer:
Different isolation levels provide different degrees of data consistency and concurrency control in database transactions.
Step-by-step explanation:
If any transaction executes at a Read Uncommitted Isolation Level, then serializability may be violated. This isolation level allows a transaction to read uncommitted data, which can lead to inconsistent results and data anomalies. For example, if Transaction A reads an uncommitted value from Transaction B, and Transaction B later rolls back, then Transaction A will have read an invalid value.
On the other hand, Read Committed Isolation Level only allows a transaction to read committed data, ensuring that each transaction only sees data that has been successfully committed by other transactions. This isolation level reduces the chances of data inconsistencies but does not guarantee serializability.
Repeatable Read Isolation Level ensures that a transaction sees a consistent snapshot of the database, even if other transactions modify the data. It prevents dirty reads, non-repeatable reads, and phantom reads. This isolation level is achieved through locking and versioning mechanisms.
Serializable Isolation Level provides the highest level of isolation, guaranteeing that all transactions are executed serially. It prevents dirty reads, non-repeatable reads, and phantom reads by acquiring locks on the data. However, this isolation level can also lead to more contention and reduced concurrency.