1) it store all data in RAM.
Qlikview loads the entire data model into RAM. As a very rough guide, the size on disk is usually about 8 times smaller than in RAM.
If you are using the QV Server, then this will occur on the server's RAM. If a second user opens the same app, then it will only add a small(ish) more to the RAM, the third, even less, etc.
or read the attached document..
you could never get a accurate calculation.
many thing are involves. one of them are user, that how many user are accessing the documents at the same time..
for example if userA opens a document and let say it consumes 100 MB, and if UserB access document at the same time, it will not Consume 100 MB, it Might consume, 60 MB, And third 40 and so on...
Read the document or make a search on community, you will get lot of information reduce the RAM usage, and approx Calculation...