The refreshes are all full refreshes. I asked about incremental and why it wasn't being done, the answer I received was that they looked into it and it might take longer.
The only reason I could think that it would take longer is on how DB Link works.
In SQL it depends on the type of connection as to where the processing takes place. One way would send the query to the source where it would process and bring back the results. The other way would bring back ALL the data from the source to the target and then do the select, writing only the requested data. But obviously it wouldn't speed things up if all the data had to come back anyway.
Can anyone confirm how the DB Link works?