What types of transaction isolation are available in Transaction Manager?

In Java's Transaction Manager (for example, in JTA or Spring), there are standard transaction isolation levels defined by the JDBC and SQL specifications. They control how one transaction sees changes made by others and prevent various anomalies.

Main transaction isolation levels:

1. READ_UNCOMMITTED

   • The lowest level of isolation.
   • Allows seeing uncommitted changes from other transactions (dirty reads).

2. READ_COMMITTED

   • Allows reading only committed data.
   • Prevents dirty reads.
   • Non-repeatable reads are possible.

3. REPEATABLE_READ

   • Ensures that data read in a transaction does not change until it completes.
   • Prevents non-repeatable reads.
   • Phantom reads are possible (new rows added by other transactions).

4. SERIALIZABLE

   • The highest level of isolation.
   • Transactions are executed sequentially, as if one after another.
   • Prevents phantom reads.

How it relates to Transaction Manager

• The Transaction Manager manages transactions and can set the isolation level via configuration or API.
• In Spring, for example, you can specify the isolation level using the @Transactional(isolation = Isolation.REPEATABLE_READ) annotation.

Example in Spring:

@Transactional(isolation = Isolation.SERIALIZABLE)
public void someTransactionalMethod() {
    // business logic
}

Thus, isolation levels help control concurrent access to data and balance performance with data integrity.