A site ID is a unique code to identify your installation of Teradata Database on Azure. Although this site ID is not required to use Teradata Database on Azure, it is required to receive Teradata support. Since Developer is free, a Site IDs is not needed for that tier.
After completing the support registration at http://www.teradata.com/azure/support/, an email is sent by the second business day from the time you registered for Teradata support. The email contains your Master Customer Record, Site ID, user ID, and password. Your Site ID begins with AZRTDB, followed by 9 characters that are determined by the Teradata customer.
Existing Teradata customers who have on-premises Teradata systems cannot use their previous site IDs on Teradata Database on Azure. You must obtain a new site ID.