The cookieDomainPeriods variable determines the domain on which the Analytics cookies s_cc and s_sq are set by determining the number of periods in the domain of the page URL. This variable is also used by some plug-ins in determining the correct domain to set the plug-in's cookie.
The default value for cookieDomainPeriods is "2". This is the value that is used if cookieDomainPeriods is omitted. For example, using the domain www.mysite.com, cookieDomainPeriods should be "2". For www.mysite.co.jp, cookieDomainPeriods should be "3".
For example, if setting cookieDomainPeriods to "2" on the domain www.mysite.co.jp, the s_cc and s_sq cookies are created on the domainco.jp. Because co.jp is an invalid domain, almost all browsers reject these cookies. As a consequence, visitor click map data is lost, and theVisitor Profile > Technology > Cookies report indicates that almost 100% of visitors reject cookies.
Note: Do not include additional subdomains as part of cookieDomainPeriods. For example, store.toys.mysite.com would still havecookieDomainPeriods set to "2". This variable definition correctly sets the cookies on the root domain, mysite.com. SettingcookieDomainPeriods to "3" in this example would set cookies on the domain toys.mysite.com, which has the same implications as the prior example.
If you notice that visitor click map data is absent, or that the Traffic > Technology > Cookies report shows a large percentage of visitors who reject cookies, check that the value of cookieDomainPeriods is correct.
If cookieDomainPeriods is higher than the number of sections in the domain, cookies will be set with the full domain. This can cause data loss as visitors switch between subdomains.
The cookieDomainPeriods variable was used in deprecated implementations prior to trackingServer to set the visitor ID cookie. Though only present in outdated code, failure to correctly define cookieDomainPeriods in this circumstance puts your implementation at risk of data loss.