How to use Oracle as a remote/local database for Drupal 7?
There is a stable Oracle database driver in Contrib: http://drupal.org/project/oracle

However, if you want to use Oracle for your main Drupal database, you will need to test each contrib module that you are planning to use for Oracle compatibility. Many still have MySQL specific SQL, even though the situation has improved a lot thanks to the new database abstraction layer.

Using the Oracle driver to access data from a secondary database for imports and so on should work fine, though.