[Zope] A couple of questions from a newbie

[Leif K-Brooks]

Hello, everyone. I've been reading up on Zope, and it's quite 
interesting; I still have a couple questions that The Zope Book doesn't 
answer, though.

First of all, is there any reason to use a relational database instead 
of the ZODB? I would think that the ZODB would get bad performance when 
filled with too many user-created objects, like forum posts; is that true?

Also, is it better for a Python script to call a page template or 
vice-versa? I would think that it would be better for the template to 
call the script so that other scripts and templates can use the script's 
output, and so that it can be cached without caching the template's 
header and footer which might be user-specific, but The Zope Book 
usually has the script calling the template.