Can you explain the concept and types of isolation levels in database management systems?

Isolation levels in DBMS define the degree of isolation of transactions from each other, that is, how much one transaction can see the changes made by another before it is committed.

Main isolation levels:

1. Read Uncommitted

   • A transaction can see changes made by other transactions even if they are not committed.
   • Dirty reads are possible.

2. Read Committed

   • A transaction only sees data that has been committed.
   • Prevents dirty reads but allows non-repeatable reads.

3. Repeatable Read

   • Guarantees that if a transaction reads data, subsequent reads will return the same data.
   • Prevents non-repeatable reads but allows phantom reads.

4. Serializable

   • The strictest isolation level.
   • Transactions are executed as if they were sequential.
   • Prevents phantom reads but reduces concurrency.

Choosing an isolation level is a compromise between data integrity and performance. For example, banking operations often choose Serializable, while analytics may use lower levels.