To maintain your application's client identity information in a clustered server environment, you must specify This.setdomaincookies="True" in the Application.cfc initialization code, or use the cfapplication setdomaincookies attribute in your Application.cfm page.
The setdomaincookies attribute specifies that the server-side copies of the CFID and CFToken variables used to identify the client to ColdFusion are stored at the domain level (for example, .macromedia.com). If CFID and CFToken variable combinations already exist on each host in the cluster, ColdFusion migrates the host-level variables on each cluster member to the single, common domain-level variable. Following the setting or migration of host-level cookie variables to domain-level variables, ColdFusion creates a new cookie variable (CFMagic) that tells ColdFusion that domain-level cookies have been set.
If you use client variables in a clustered system, you must also use a database or cookies to store the variables.