Container-Managed Transaction Demarcation
You've spent the last three days writing and deploying EJBs without really having to worry too much about transactions. This isn't to say that there have been no transactions in use; far from it. Every interaction with the database performed in the case study has involved transactions. However, the Session and Entity beans deployed have used container managed transaction demarcation (here referred to as CMTD, though the abbreviation isn't used in the EJB specification). This section discusses the support provided by J2EE for CMTD.
Information in the deployment descriptor indicates when the EJB container should start and commit transactions.