4.6C upgrade to ECC6 AND informix to DB2 conversion

Hello Experts,

We are about to embark on a DB migration and SAP upgrade project with one of our clients.

The current system is 4.6C , Informix 7.31 running on AIX 5.3 and will upgrade to ECC6 , DB2 V 9.7 (if it's available by the time the project kicks off).

The plan is to perfom the DB migration on 4.6C first and then only Upgrade to ECC6.I found a document on SDN regrading the compability between 4.6C and DB2 V 9.5.

I would like to know what the best way of doing this is.I have gone through the R3 Homogeneos System Copy document and it states that we'd have to use the R3load method for the copy .

Is there any other way of doing this besides using the Homogenous system opy method? Has anyone else ever gone through this type of upgrade ? What stpes were followed during the upgrade?How much downtime was experienced?Please share the issues you experienced during the upgrade and tips if any.

Thanking You in advance for your responses.

Nelly