Hi!
You should be able to make this transition without too much headache, but the error -1 means "not the owner", and Informix is pretty adamant about having the proper ownership ("informix:informix") and permissions (rwx on dirs, rw- on files) over the file structures it deals with, because it relies on that layer instead of having its own parallael universe of security (actually a good decision, IMHO, because it foregoes an extra layer of management/complexity on your behalf).
Other questions that might help others assist you as you try to get through this:
Which versions of the OS are you using (including kernel and gcc on RedHat)?
Which version(s) of Informix are you using?
Providing that info up front often helps get faster responses, because it helps your readers filter themselves out (or in) in terms of whether they might know something helpful to you.
Good luck!