tablename_delete is used to DELETE a record from an XFD file. The parameters passed to the stored procedure are the values of the primary key, in the order they are listed in the XFD.
Based on the Sample XFD, you might want to create the following stored procedure for deleting records from a file:
create procedure ftestdat_delete @ft2_key char(4) as delete from ftestdat where ftest2_key = @ft2_key grant execute on ftestdat_delete to public