Problems with Informix_OL and PowerBuilder

Hello there, I'm looking for a DBMS and an application development system. At the moment I'm playing around with the Informix Online Workgroup Server 7.1.2 for NT demo version and PowerBuilder 5.0 and face some problems, that I do not understand (I'm new to databases in every respect): - I have setup a simple test database using the Informix tools. - I have established an ODBC connection to PowerBuilder. - I can open the test db from PB and work on it (add columns to table definitions for example). However, there are things that I can't do from within PowerBuilder: - I can't delete columns from table definitions (-> syntax error). - I can't see the foreign keys I have defined in the test db. (I can see and edit them when I use the Informix tools, however.) - I can't add foreign keys (-> syntax error). I would be very glad if someone could tell me, whether these problems are typically related to the components I use, or my ignorance or some other reasons. TIA Erwin