Change in AUTO_DUPLICATE_LVL

Hi,

We want to change in our OCS 2.1.2 server the AUTO_DUPLICATE_LVL option. Now we have checked hostname, serial and macaddress but we want to check only serial because everytime a user changes its hostname it generates a new record. Will the server automatically merge all the records? If a computer does not contact again, what will happen? If in the future we want to change it again to hostname, serial and macaddress, will it work? If we only have serial and a computer does not have a serial field or is empty, what will happen?

thanks!