There is disclosed a method, apparatus and a computer code to maintain databases. In the method a first database containing information of a usage of a frequency spectrum is maintained for a first geographical area by the apparatus. Information is received from a second database apparatus on a second geographical area. The first database apparatus determines whether said first geographical area and said second geographical area are at least partly overlapping. A linkage table is maintained to provide an indication on the result of the determination, wherein said indication is indicative of whether said first geographical area and said second geographical area are at least partly overlapping.