Upgrading from Informix 5.x to 7.x and AIX 3.x to 4.x

Hi All My client is planning to upgrade from AIX 3.x to 4.x and simultaneously = from Informix 5.x to 7.x. The database is about 1GB and currently split = across 4 disks. The system is an OLTP type of system, running on = Informix 5.x and AIX 3.x. Currently the database resides on a server and = is accessed from a client machine using Informix-Star. I was wondering if anybody has done something similar before and what = are the things I need to watch out for in terms of compatibility and = performance. Any help/info/pointers would be appreciated. If you want more = information, I would be happy to find out more and let you know. TIA Sujit Pal