The CMDB provides overview, better change control and proactivity. Activities in an IT department/Service department affect many different areas: people, PCs, software/hardware, equipment, components, etc.
The CMDB gives you the whole overview in one place, at the level your department needs.
In the CMDB you can include all the services provided by the department and/or all servers/software/pcs etc. that support the services.
Whatever you choose to include, it is very important that it is at a level that can be maintained. Hardware can be updated automatically via More Service Discovery.
This example shows how easily you can identify which systems, services, and customers are affected by a change made to the server "APPX01".
In the example above, there are both relationships and dependencies. Black arrow up/down shows that there is an parent/subordinate dependency between objects. In the example, we see that the accounting system service is dependent on the Visma application to work. Visma is again dependent on the server APPX01 to work. We also see that the customers ExtraBra AS and Saras Sysaker use the service. Customers have no black arrow and hence no dependency, only a relationship.
CMDB also has a graphical depiction of dependents, which makes it easy to see how the objects are connected: