Delete previous XML data when we import a new XML

We use the XML source pane for visualizing the information we need. And we map tabs from the source task pane whichever we find necessary. 

 

But every time I import a new XML file, it replaces the previous XML data only if the current number of rows are more than the previous rows. 

 

So if the number of rows from the previous XML are more than the current XML, the data from the previous XML is retained. How to avoid this?