Reservations are a critical feature in the DHCP server. Reservations are generally used for centralized static IP address assignment for critical machines. This way the IP address of the critical machines which serves critical functions in the network will not have a dynamically assigned IP address which can change over time. The reservation manager is a tool which will help solve typical reservation-related problems which the network admins might face.
Here is an article which introduces the usage of the Reservation Manager tool：
Reservation Manager - A tool to manage reservations
The tool can be downloaded here: