It lets you track message at certain points in their life cycle by invoking custom code from user exits while the message is passing through the message flow.
它允许您在消息通过消息流传递时调用用户出口中的自定义代码，从而在消息生命周期中的某个点跟踪消息。
2
At the node level you can track the passing of the message from one node to the other. Consider the following example scenario.
在节点级别，您可以跟踪消息从一个节点到另一个节点的传递。
3
Most people regard overtaking as meaning cars passing each other on the track, during the race.