When merging two databases it is VERY IMPORTANT to use identical IDs ('name') for identical species and different IDs for different species. If not, data of different species will be merged or overwritten.
Species are identified using the accession number and (optionally) one additional field. If you use an additional field, a different NAMESERVER is used to synchronize species IDs.
Because of different NAMESERVERs, merging two databases is only possible if both databases use no additional field or if they use the same field.
To synchronize IDs of all species in both databases, press the 'Check IDs ...' button to open the 'Synchronize IDs' window.
Make sure both databases use the same additional field.
Press the 'Synchronize' button to synchronize species IDs in both databases.