CMT == Container Managed Transaction. When CMT is used, the EJB Container controls the transactioning for the specified EJB or method. The scope of the transactions in CMT are set declaratively in the EJB's deployment descriptor. CMP == Container Managed Persistance. Entity Beans come in two flavors: BMP and CMP. With BMP, the developer is required to write all database access logic for persisting entities. With CMP, the EJB Container handled the persistance of entities automagically. CMR == Container Managed Relationships. One of the things that happens frequently when using Entity Beans is the need to form relationships between the various types of Entity Beans. When using BMP, all relationships must be explicitly managed by the developer. When using CMP, relationship management can be regulated to the EJB Container. There is no relationship between CMT and the other two. However, there is a strong relationship between CMP and CMR. In fact, in order to use CMR you must be using CMP.
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