[Zope] ZODB vs SQL

[aborel]

In "Choosing to store data in SQL vs ZODB" located 
http://www.zope.org/Members/anthony/sql_vs_ZODB

i read :
"Will the data be frequently changing?

If the data is going to be frequently changing, then it's not a good 
idea to put it in the ZODB.
Every time the data changes, a new record will be appended to the 
Data.fs file - this could become a problem very quickly."

Does that mean that the changes AND the old version of the object are 
kept in ZODB ?


If it's true, is packing a good way to throw away the old versions of 
the object ?


If Not, What are the good ways ?


Well i hope that's my last question for today.

Thanks

Andre