Uniqueness Database Files (UDFs) are an extension of the answer file functionality. A UDF has a structure similar to that of an answer file. However, the UDF begins with an additional section in which uniqueness IDs are specified and mapped to sections in the UDF. If a uniqueness ID is specified in the winnt or winnt32 command, any values specified in the sections associated with that uniqueness ID override the values in the sections in the answer file that have the same section names.
One UDF can have numerous uniqueness IDs, and each uniqueness ID can specify a slightly different configuration. For example, you can have a uniqueness ID for each computer in your organization, with a different computername for each uniqueness ID— all in one UDF.