Can I sync an existing database using a .dmp file?

I have two oracle databases (production and lab). When I created the lab database I imported a .dmp file from production to copy the data. Now that the database has been running for a while the data is out of sync and I'd like to import again. What's the easiest way to do this? I tried using imp again but it shows errors now since the tables are already there. I could delete the data files and re import I suppose. Edit: This is what I've tried: $ imp user/password file=MyExportFile.dmp following statement failed because the object already exists: CREATE TABLE ... ... Import terminated successfully with warnings.