Drupal 6: Feeds mapping node taxonomy term I using feeds module for import data from xml to node.

I have XML: 

&lt;root&gt; 
&lt;item&gt;
&lt;title&gt;Example 1&lt;/title&gt; &lt;!-- map to node title--&gt;
&lt;body&gt;Body of example 1&lt;/body&gt; &lt;!-- map to node title--&gt;
&lt;term_name&gt;My_term&lt;/term_name&gt;
&lt;term_tid&gt;15&lt;/term_tid&gt;
&lt;/item&gt;
&lt;/root&gt;



SELECT tid, vid, name FROM term_data;
tid vid name
15  19  My_term


If I map &lt;term_name&gt; to my node taxonomy term (and term name exist) its working. 
But If i map &lt;term_tid&gt; to my node taxonomy term (and term tid exist) it's NOT working. Why? 

Thanks for helping
before importing nodes from a site that contains taxonomy terms , try first to import all taxonomy terms ( you can use taxonomy manager ).

Feeds will add a term with a new tid if It not exist , not the same as tid of the site from where you export