If you try to delete an application or a SendPort, you might find that SendPort is used on an EDI Trading-Partner (party).
There is no easy xref in BizTalk to show you which party might be tied to that send port. Usually the naming conventions will help, but not always.
This SQL query gives you the cross-reference.

<pre>
USE BizTalkMgmtDb

SELECT 
   party.nvcname [PartyName],
   application.nvcDescription [Application],
   sendport.nvcname [SendPort]
FROM bts_sendport sendport
INNER JOIN bts_party_sendport partysendport ON partysendport.nsendportid = sendport.nid
INNER JOIN bts_party party ON partysendport.npartyid = party.nid
INNER JOIN bts_application application on application.nid = sendport.nApplicationID 
ORDER BY party.nvcname,  sendport.nvcname
</pre>