Thanks for the reply leone.
I have Aperture 3.6. I have been able to open Library chooser panel and can see my library in the aux drive there but on double clicking, I get a message - the file system of the library volume is unsupported. I don't know how to move the library to a drive that is formatted MacOS Extended (Journaled). I have moved the library into my macbook and tried again - same message. ( I upgraded to Yosemite 2 months ago) Could you let me know how to to do the upgrade?
Just to clear on my storage - I found Vaults a bit confusing so I drag each Aperture library to an aux driver. When I want a library I don't open Aperture in my macbook - I double click the library in the aux drive and it opens Aperture with the full library and folders as I last worked on them. I close Aperture and do the same operation to open another library from the aux file to open Aperture.
Is this storage method a problem when I move from 2.1.4 to 3.6?
I am in Malaysia at the moment and my Aperture 2 disc is in Europe, where I will be in April. At worst, can I re-install Aperture 2 again and run both Apertures or is Aperture unsupported by Yosemite in terms of re-installing.It would be great to have all my libraries going back several years now being available on Aperture 3.6