IMPORTANT: Informix to Oracle 8 Moving?????????!!!!!!!!

I have partner which is interested to move from Informix to Oracle. Oracle Database is well known for me. But, can anyone tell me which problems or similar unusual difficulties has in this task. In informix DB is just pure relational model, but I don't know does exist anyone difference in concepts in Informix objects and Oracle objects. Which things must be gained in focus that I can resolve problem of migrating.
Where I can find infos about Informix specifics and related things which I have to attract.
I plan to use Erwin for reverse engineering of model, but is it enough. Client is MS Access over ODBC, what is not difficult. Please, send me your hint.
Thanks,
Mladen.

Note: Send me your hints(answers) to adress belove!!!!!!!!!! Thanks again.

          Mladen Vidic
  mailto: mladen_at_matf.bg.ac.yu
http://alas.matf.bg.ac.yu/~mladen/

           Oracle OCP