@Debayan Mukherjee​ the error code is : undefined function: my_udf_name. This function is neither a bulit-in/temporary function nor a persistent function that is qualified as spark_catalog_.default.my_udf_name.

To my understanding, the dbuils.notebook.run triggered a separate job, which defined and registered a function, but both jobs were executed on the same cluster, so they were within the same spark session, and registered udf is tied to the spark session. Why the masternote cannot call the udf defined in the child notebook here?

If I use magic command %run, it will be executed in the same job, and masternote book has no issue calling the registerd udf defined in the child notebook.