In present-day industrial control systems responsible for effective and safe operation of nuclear power plants (NPP), the databases of the upper level play a crucial role in process monitoring and control as they acquire, process, and present to the operator the data from all the lower-level systems. Moreover, the air-gapped separation of the upper level makes them extremely valuable for the entire manufacturing management. The specific feature that should be taken into account when dealing with databases of upper level control systems is that they are not perfectly stable and due to the modifications being introduced in lower-level systems subject to changes at all stages of the life cycle. The problem of making changes to the databases combining information of all lower-level devices and so being highly complicated happens to be particularly serious. The article considers the databases of NPP upper level control systems and delves into the problem of making changes to them. A brief overview of the upper level control system illustrating the importance of databases is presented. The description of working databases is provided, their characteristic features are highlighted and the basic principles of the methods for making changes to them are disclosed.