What is the best purpose of the TOP domain?

The TOP domain in ServiceNow’s domain separation model serves as the core data domain and the parent domain for the mapping diagram. This is because the TOP domain is typically owned by the service provider and has control over all other sub-domains within the instance1. It is the highest level in the domain hierarchy and is responsible for the global rules, processes, and administrative tasks that affect all sub-domains1. The instance administration is given to the global and top domains, with the global domain setting the overarching rules and the top domain managing the specifics for each sub-domain1.

Domain separation in ServiceNow is a mechanism to separate data, processes, and administrative tasks into logical groupings called domains. This allows for control over several aspects of this separation, including absolute data segregation between business entities, customization of business process definitions, user interfaces for each domain, and maintenance of some global processes and global reporting within a single instance2.

In summary, the TOP domain’s primary purpose is to act as the core data domain, providing a foundation for domain separation and ensuring that the service provider can effectively manage and control the entire domain structure within the ServiceNow instance.