problem when transfering file

I want to transfer file to another compurter, but when I tried to open file on another compurter, the error message shows 'Schema localdb: Disconnected" . How to solve this? Thanks.

Dear Jiye,
from the screenshots provided with much information missing it is hard to assume what is happening in your specific case.
Personally, the 'Derby disconnected' window I have seen only wen I tried to connect to a Derby database multiple times at once, such as IJC and Services inside IJC. Derby DB allows only one connection at a time, therefore the best way how to transfer Derby DB based project including the data is to make an archive of the project and decompress it in the other location, which can be useful also as schema backup (see the documentation here).
Also, you might get into unexpected issues when transfering data between UNIX-based and Windows-based systems, when the file path signs \ (for Windows) and / (for UNIX) are mixed up and in the end not understandable.
The recommendation on accessing database entries from multiple locations is to used a remote database such as Oracle or MySQL, the list of supported databases can be found here.
I hope this helps and if not, could you please provide us more details on which file you need to transfer, what system do you use, IJC version and at least the detailed error message.
Best regards,
Karla