Migration from 3.3 to 16.1

Hello Guys.

currently I'm in progress to migrate a smoothly running Kolab 3.3 
community edition with installed multidomain-patches to current Kolab 
16.1 community.

My planned migration path is roughly:
1 install a fresh server with bare 16.1
2 tweak new server for multidomain functionality
3 copy over the imap store from old server to new server
4 copy over the ldap database
5 copy over the sql database

So far i've reached top 4 in my plan, which means i've migrated the ldap 
onto the new server and i'm able to login via roundcube. I can see all 
messages, calendars, shared ressources and folders, sieve scripts 
function properly as far as i can see. wonderful :)

But what i'm unsure about is top 5 (migrate SQL).
Can someone tell me if there have been sql changes between kolab 3.3 and 
kolab 16.1? Can i simply sqldump the old database on 3.3 and import it 
into 16.1?
Do i need to copy the SQL database at all? I don't know what it is used 
for anyway, is it the cache? does ist store user configurations?

Can someone with more deep knowledge enlighten me?

Thank you very much :)