Hi S.Jeeva,
If you had our DBXL Web Service, you could use our Bulk Edit tool to do that.
In your case, you can either a) update all of the XML files and resubmit them, or b) update the SQL data and change your form to query it on open. Neither solution is simple, but they are both doable. I guess the key question you have to ask is whether or not your users open the XML files or open the XSN and populate from the DB. I don't know how your form works. If it is populating from the receive data connection, you should take option (b). On the other hand, if they are opening XML files and submitting, you will have to edit the XML files in place and resubmit them all (a). We have tools to do that but it's a little tricky since it depends on how your Web Servie is written (does it support edits and subsequent submits for XML files?). Too bad you didn't use our Web Service. Then, it would have been trivial.
:)