Persistence operations need to be performed in a transaction context. Managed entities that are modified are synchronized into the datasource at transaction commit time. Therefore, a transaction spans the modifying action, and typically the whole business use case.

If the boundary is implemented as EJB, a transaction is active during the business method execution by default. This matches the typical scenarios for JPA persistence being involved in the application.

The same behavior is realized with CDI managed beans that annotate their methods with @Transactional. Transactional boundaries specify a specific behavior once the business method is entered. By default, this behavior defines that a transaction is REQUIRED; that is, a transaction is either created or reused if the calling context is already executed within an active transaction.

REQUIRES_NEW behavior will always start a new transaction that is executed individually and resumes a potential previous transaction once the method and the new transaction has completed. This is useful for longer-running business processes that handle a great amount of data that can be processed in several, individual transactions.

Other transaction behavior is possible as well, such as enforcing an already active transaction or not supporting transactions at all. This is configured by annotating business methods with @Transactional. EJBs implicitly define REQUIRED transactions.

RDBMS systems integrate well into Java EE applications. Following convention over configuration, the typical use cases are implemented in a productive way.