import and export using impdp/expdp in oracle10g/11g

I have two databases, one is produ开发者_开发问答ction and second is a test. I want to export from production database and import into test database. My production db contains many users/schema out of which only few (<10) schemas contain actual objects. First time, i did a successful full export and full import into my test system without any problem.

The idea is to do this on a periodic basis maybe once in couple of weeks. How can i do this process without creating a whole new test database again doing the re-import??

In impdp there is the option to import data only using CONTENT=DATA_ONLY http://download.oracle.com/docs/cd/B19306_01/server.102/b14215/dp_import.htm
Also have a look at TABLE_EXISTS_ACTION (which already defaults to APPEND if using DATA_ONLY)