Delete UDFs
To delete a user-defined function:
1.Double-click the title bar of the user-defined function on the mapping.
2.Click the Erase 
button in the top-right corner of the Mapping window.
3.If the function is used in the currently open mapping, a dialog box is displayed.
Click Yes if you want to delete function and replace all instances where it is called with the function's components. This lets you keep the main mapping valid even if the function is deleted. However, if the deleted function is used in any other external mappings, those will become not valid.
Click No if you want to delete the function and all its internal components permanently (in this case, all the mappings where the function is used will become not valid).