The size ? I don't believe we have limits on size (except disk space).
When you are dealing with large QVDs you can instead and should consider loading and storing them in segments.
So if you pull 3 years of data into one QVD like this
Table:
Load *
from <source>;
store .... Table.QVD
Then consider using 3 different load statements to store 3 different QVDs.
A really great benefit to this is that you can execute the three loads and stores in DIFFERENT QVWs to accomplish a parallel load to support a tighter schedule.
Your final app will of course re-concatenate the 3 QVDs back into one table, but that action is very fast with qlikview.
Table1:
Load *
from <source>
where year =2014;
store .... Table1.QVD
Table2:
Load *
from <source>
where year =2013;
store .... Table2.QVD
Table3:
Load *
from <source>
where year =2012;
store .... Table3.QVD
