We have not centralized the databases, but the logic behind no overlapping databases is that we don't collect the same data in different databases. For example, if we have a population registry containing basic information about citizens and residents, then when police forces create their own police database, we don't allow them to collect the same basic information there. They have to take the most recent information from the population registry.
The idea is that different state institutions have authority over certain data. If they are allowed to collect this data and keep it in their database, then nobody else can collect and keep the same data. In this way, we keep the data in order at the state level.