Transaction Handling..

we have to support transactions in our ASP based application.
What we do is we have most of the database stuff implemented in COM (using VB).
DML operations are handled in COM we just pass the SQL query as a string to COM method and then that method is handling the database interaction.
The issue which i am facing is whether to implement Transaction support at ASP level or in the COM? What all benefits i get by implementing either way ....
Could somebody help regarding material, technical articles or has somebody faced the same situation before?
Thanks in advance for your help...