Precautions during the implementation are as follows:

• A container invokes the afterBegin method, beforeCompletion method, or afterCompletion method only when the javax.ejb.SessionSynchronization interface is implemented in the target Session Bean (or its parent class) or when the annotation is specified in the Session Bean.
  If both, the implementation of the javax.ejb.SessionSynchronization interface and specification of annotations are implemented when developing a Session Bean, implementation of the interface is given priority.
  
• If you specify the same annotation for multiple times in a Session Bean class, we cannot guarantee which method from among the afterBegin method, beforeCompletion method or afterCompletion method specified for multiple times will be invoked by the container.
• If you specify parameters not conforming to the annotation rules, the application fails to start and the KDJE42039-E message is output.
• You can invoke the methods for which the processing time is set using the @AfterBegin annotation, @BeforeCompletion annotation, or @AfterCompletion annotation directly from the client machine, in the same way as for other business methods. However, generally, the callback method is not to be published on the client machine as a business method. Therefore, we recommend declaring a value other than public in the access modifier of such methods.