detect changes on a table

Hello,

I have to create a database (A) based on the content of another one (B, hosted on oracle) which hosts informations on students (and driven by a commercial application).
If it will be simple to populate db A initially, I don't see a way to keep the data in sync with B as updates will occur.

Do someone here have an idea about that ? Is there a way to detect updated records for a given table ?

Thanks in advance,

-- 
Artturi