According to the book
Jboss Seam - Simplicity and power beyond Java EE, page 129, @TransactionAttribute@ is for EJB3 entities, not for POJO enties:
In EJB3 session beans, you can set the transaction attribute for any method using the @TransactionAttribute annotation. [..] In Seam POJOs, method level transaction demarcation is not available
If you are using POJO entities and according to this page, the transactions are managed using the transaction manager, configured using the TransactionPhaseListener from faces-config.xml, or by adding the @Transactional annotation to the method.