How to transfer large amount of data from Win/Sybase IQ to AS400 DB2 ?

Hi all,
we have implemented datawarehouse in Sybase IQ.
Nowadays we are preparing data interface (small datamart) for reporting
system implemented in Cobol/AS400 DB2.
We need to (on daily basis) transfer large amount of data (e.g. GBytes)
from Win/Sybase IQ environment to AS400/DB2
I thing, that solutions based on OLE DB / ODBC / JDBC will be useless
form the picture of performance.
What do you thing about possibility of generate CSV files, transfer via
FTP to AS400 and upload to DB2 ? Is it speedy enough? Is it good
choice? Advantages/disadvantages?

Is there another opportunity - I don't want to use third party
tools/middleware ?
Thanx for any advice.

.