Can you name the existing levels of transaction isolation in database management systems?.

The main transaction isolation levels in database management systems are:

1. Read Uncommitted — a transaction can see changes made by other transactions even if they are not yet committed (possible dirty reads).
2. Read Committed — a transaction only sees committed changes, preventing dirty reads.
3. Repeatable Read — guarantees that data read in a transaction will not change until the transaction completes, preventing non-repeatable reads.
4. Serializable — the strictest level, transactions are executed as if they were sequential, preventing phantom reads.

Each level balances between performance and data integrity.