Migration from 2.0 to 3.0
From OpenKM Documentation
Due to the complexity of the migration process and the lack of documentation and old source code due a to a hardware failure, we recommend export the repository and import it again from the new OpenKM installation.
If you are really interested in a real migration process which preserve old document versions and other metadata, please contact us and we will study your particular case.
Sorry for the incovenience.