[Zope3-Users] zodb objects backup

[Chris Withers]

Hi Shaun,

Shaun Cutts wrote:
> Ah -- very nice: so Data.fs *is* a transaction log. 

Yup, and a very simple, robust one at that ;-)

> In theory an RDBMS
> with write ahead logging is still more secure because the transaction
> log is only backup, and the rest of the database is another copy of the
> current state (though not with undo capability).

Well, if you worry about this, fork out for ZRS, which writes all your 
transactions to multiple back end storage servers...

> But with replication, this issue is taken care of. (Too bad replication
> isn't part of the core functionality....)

You can always do application-level replication ;-)

> Section 3.1... so ZODB is effectively doing MVCCS and with per-object
> locks to resolve conflicts. 

Someone else explained how Zope 2.8+ is now even better with this :-)

>(Question: can one explicitly lock an object
> without changing it? I guess just setting _p_changed?)

No, 'cos that would also mean that a copy of the object got added to the 
end of Data.fs when the current transaction is committed, which is done 
by Zope's publisher...

>   3) general lack of query language potentially problematic for
> datamining

catalogs are your friends...

cheers,

Chris

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