K2 update 4.6.1 released recently includes an Oracle Service object. This extends K2′s reach to Oracle databases. This service object allows you to create SmartObjects from Oracle database objects much like the Dynamic SQL Service object. Find out more about it here and if you are keen to connect to Oracle using SmartObjects do apply this update.
After applying this update make sure that you have installed the Oracle OLEDB driver for your version of Windows. Then restart the K2 service. You can now use the SmartObjects tester tool and you are up and away talking to Oracle :)
Also, starting with K2 4.6.1, there is only one installer which can be used for clean and upgrade installations. The installer always contains the latest update.