Hi Lorne,
It sounds like a snapshot is the best approach...From a DBA perspective...
I recently had the requirement my self for something similar. The reason for this being that a failure on one system would not prevent the other system from operating....
In the case currency data from an ERP system...

The way it works is....
1)I have writen a package from integrating in and out all in PL\SQL


-In your case you will create a UNIX cron job that runs a query throught a great function:...
That creates a ; seperated file based on an SQL query...

-Then you open the file at the other end and read in it's contents..

I have done this in a general way so I wonøt explain it in great detail hopefully you get the idea...
Rather I'll say..I would be happy to share all the code if you think it will help...

Problem is I had to write a DLL to to delete, copy and move files and retrun the oldest file from within PL SQL so
it will only run on Windows NT. You would have to create something similar for a UNIX platform...But if you only use one file it's s simpler problem...

One other idea could be to look into Oracle Integration Server...
I checked it out briefly and was very impressed...