The configuration management application in ServiceNow is used to build and maintain the logical service configurations of the infrastructure and applications that support a service. In order to build applications surrounding the configuration management application, it is important to understand the architecture of the configuration management tables.

The logical service configurations are stored in the Configuration Management Database (CMDB), and are mapped to the physical inventory in your organization. The CMDB consists of entities called configuration items (CI). A CI may be:

• A physical entity: Such as a computer or router
• A logical entity: Such as an instance of a database
• Conceptual: Such as a payroll service

The parent class of all CI classes in ServiceNow is the cmdb (base configuration item) table. It has some set of fields that are relevant to all configuration items. The cmdb table is extended by the a table named cmdb_ci (Configuration Item). There are over 90 tables/CI class definitions that extend the Configuration Item (cmdb_ci) table, and thus they also inherit the fields from the base configuration table (cmdb.) This is illustrated in the following image:

To see the relationships between tables (classes), we can always refer to the schema map. The Database Instance and Application Server tables extend the Application class, which in turn extends cmdb_ci and again extends the cmdb class.