In CMS7, there is a new table for each dataclass - History Delta Table, that is prefix InvHistDelta_xxx
In addition the usual CMS6 InvHist_xxx

I do not find any information in KB, Connect or User's guide ... ;-)

I hope this will solve the current CMS 6 History issue, that is collecting & stroring every data NS receives, all the same the same value the previous one... Not really optimized ! Isnt'it ? ;-)