Duplicate entry inserted in the SQL database while calling an ASP

Hi All,



I hope I posted this inquiry under the correct forum.



To start off, I have been working on a bug where duplicate inserts happen
when calling an ASP page that does the DB insert processing. We have a
software where a user is given two options to register: 1) via the software's
panel and 2) over the internet. Option 1 is known to be the "Auto
Registration" - user is requested to fill out a form, supply the details such
as customer name, SN(serial number), site code etc., then clicks "Register
Now" button. A background process (implemented in C++ socket programming) is
started that sends out a request to an ASP page. This ASP page
(RegModule.asp) does the registration process: it does checks like SN
validity, maximum of number of allowed registrations reached, etc. If the
conditions were satisfied, then it inserts the sent values in the DB. In the
event that the website doesn't send back a "200 OK" response, the client's
software panel retries sending a request to the server. The retry is done
twice, and if still unsuccessful, prompts the client error messages like
"Auto Registration has failed" or something like that. There were some
records that have duplicates - every field are exactly the same up to the
seconds of its dateFirstRegistered field. I was asked to investigate how did
this happen.



I have made a number of inferences like:



1. Did the client clicked the "Register Now" button a number of times?

- This is not possible because the moment the "Register Now" button is
clicked, it becomes disabled.



2. How about disabling the connection retry?

- The rate of successful registration will be too low.



3. What if: The ASP page is called on the first request, began processing up
to the point where it assigns the query values (customer name, serial number,
etc) in the fields of the recordset when suddenly the connection is
interrupted. The software control panel then tries again to connect and send
out a second request. The second request catches up to what the first
request was doing before the disconnection, and at almost the same time they
both inserted their records into the database.



Is inference 3 possible? Or could it be that the both request were processed
on different threads?



Hope someone could shed some light on the matter. Thanks in advance!

.