>I checked out the thread, thanks. My problem is that the Key Field is a varchar2 data type. The discussion in this thread addressed options where non-key fields were varchar2's.

Then you have zeroed out all your options. I suggest adding another column to the Oracle table[s] and use integers as your surrogate PK. Otherwise you have to change to data type of the key field to CHARacter. PK data types of varchar2 are generally a bad idea.