Hi Gary,visitorID in data warehouse is the concatenated values of
post_visid_high and post_visid_low, two columns stored in a report
suite's raw data tables. The combination of these two columns provides
the main source of identifying a unique visitor, however it is not the
only method. Custom visitorID's can be used, as well as using a
combination of IP address and user agent if a visitorID cookie cannot be
set.