[ZODB-Dev] Newbie ZODB Questions

[Casey Duncan]

On Monday 17 September 2001 04:54 am, Jennifer Flake allegedly wrote:
> Hi There,
>
> I have never touched Zope (so I apologize for my newbie questions), but
> my company is planning on using it in our next development project.  I
> would like to get information on the data storage and its maintenance
> requirements.  I hope that someone on the list can help me get answers
> to some questions about the care and feeding of ZODB.  I've been an
> Oracle DBA for the last few years, so most of my questions are concerns
> about storage, failure modes, loss of data, scalability, etc.
>
[snip]

> (10) How does the rollback of a transaction work? (do I have to rollback
> all of the transactions that occur after the transaction that I want to
> rollback, too)?

Only if futher transactions modify the same object(s) again.

> (11) If I am "reading" an object, do I continue to get a read-consistent
> view of it, even if someone else performs a write to it, while I am
> reading it?

No, at this point it is possible to get ConflictErrors on reads (due to dirty 
reads), although I believe this is detectable.

You can use versions (long running transactions) to mitigate this though.

> (12) If my server slams down from a power outage, will Zope be able to
> recover itself gracefully when I restart it?

Because the ZODB file is only appended, it is very durable. Worst-case you 
would have to truncate the last transaction if it was only partially written.

>
> I'd appreciate any other information/experience that anyone on the list
> can offer.  Again, I'm sorry for the barrage of newbie questions.
>
> Thank you,
> Jennifer

hth,
Casey Duncan