Migrate unix version 8 to version 9

i have a program writing in PRO C which currently running in unix version 8 tie with oracle 8i, but in the future company gonna migrate this OS to version 9.
Anything i have to prepare for my PRO C program to run in unix version 9? or anything would that impact my program couldn't run well?
what is the different between this 2 version?

Not much of a difference in Solaris perspective. For Oracle, Im not sure. Its best if you can setup a test machine, install Solaris 9 and Oracle 9i example and test your applications if that works. That will give you the best answer

Can anyone provide me any posibble causes that can cause my PRO C program unworkable in the new unix server? or anything i have to take care about??
as this is the first time i'm doing migration, so worry that things might unworkable.
thanks.