[Zope-DB] Questions on DAs and TAs

[Martin Gebert]

Hi all!

For further work on Zope and DB connectivity I'd like to ask some 
questions which I need to clarify. I beg your pardon if they've been 
asked and answered already; hints for ressources are very welcome.

- Are there developers documents on DAs, esp. API references? I found 
two docs of petrilli (Roadmap for Zope Database Adapters 
<http://www.zope.org/Members/petrilli/DARoadmap> and How to Write a DA 
<http://www.zope.org/Members/petrilli/WritingADA>) which should give me 
the basics, but they seem to be a little outdated (from 1999/2000), so I 
wonder if there are more ressources on this subject?
- As I understand from reading some relevant postings in the archives of 
this list, RDBMS transactions in Zope are bound to the Zope TA concept, 
where TAs start and end with building a DTML document (correct/put too 
simple?). Are there any possibilities to force TA management by 
commit/rollback actions via the DA? (How) Can I manually rollback if 
something in a script fails? The ZopeBook says less more than nothing 
about that subject... :-(
- Did I get it right that (explicit) locking has to happen in Z SQL 
Methods? Having experience with Oracle locking mechanisms only, I wonder 
if that offers independence from different DBMS's (e. g. migrating a DB 
from, say, Oracle to MySQL, and having to change the Z SQL Methods due 
to different locking paradigms instead of simply setting up a new DA; 
hope you can follow what I try to express...). Are there no methods for 
locking in the DA API?

Thank you for reading; all hints on this subject are very welcome. 
Probably more questions to come...

Martin