I have a customer for whom I am building a data warehouse solution using SQL server 2008.
Source data comes in many forms including SQL Server 2000, SQL Server 2005, flat files (csv), Excel and Informix.
SSIS handles connections to older versions of SQL Server perfectly as expected and does a pretty good job with Excel and flat files but INFORMIX is a major pain in the backside and, as expected, neither Microsoft or IBM are particularly helpful.
The data warehouse server in question is Windows Server 64bit and my development machine is Windows 7 professional 64 bit but you cannot just install 64 bit INFORMIX ODBC drivers as Visual Studio (BIDS) is 32 bit.
If you simply install the 64 bit INFORMIX ODBC driver you will see the driver in the ODBC manager but you will not be able to use it. If you try to install the 32 bit driver from the IBM site then it will baulk stating that it is incorrect version for your system. Installation of an older 32 bit driver will work and can be administered via C:\Windows\SysWOW64\odbcad32.exe but you might end up with the “INFORMIX 3.32 32 BIT” driver which just does not work. What you need is the “IBM INFORMIX ODBC DRIVER” from the 32 bit SDK.
Once you have the ODBC driver you will also need to set up the connection and for this you might need to learn about SETNET32, the services file in Windows, the SQLHosts registry entries and you might be just a little confused about how to create the connection in SSIS as it is a little different to all the other types of connection.
Rather than repeat an already excellent article I suggest you follow this link to an excellent step by step installation and setup guide from Dinesh (DSP).
Connecting Informix databases through SSIS