Setting and Removing Breakpoints on a Transformer
You can set a breakpoint on a transformer in a MAP step. When you execute a service that contains a breakpoint or calls a service that contains a breakpoint on a transformer, the service is executed up to, but not including, the designated breakpoint transformer.
Transformers in a MAP step execute in an arbitrary order. You cannot assume an order of execution. Consequently, some of the transformers in the MAP step might execute before Designer reaches the breakpoint, even if the transformers appear below the breakpoint in the Pipeline view. Likewise, transformers above the breakpoint might not execute before the breakpoint is encountered and the debug session suspends. These will execute when the debug session resumes.
You set or remove a breakpoint on a transformer by toggling the breakpoint state.
To toggle a breakpoint on a transformer
1. Open the flow service in which you want to set a breakpoint.
2. In the editor, select the MAP step containing the transformer that will function as the breakpoint.
3. In Pipeline view, right-click the name of the transformer that will function as the breakpoint and select Toggle Breakpoint. Designer displays 
or removes next to the transformer name.