Please keep this on the list; the collective list community far outsmarts just me, so give them a chance to give input too. On 20 Nov 2006, at 14:29, Marco Bizzarri wrote:

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Yes, it is perfectly legal. All attributes starting with _v are considered volatile and won't be persisted, including dictionaries stored as such attributes.

Sorry, I did not explain well: I'm not using _v_ attributes (because they are not transactional, basically).

You cannot have both transactional and volatile, as transactions only apply to ZODB-stored (persistent) attributes.

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Is it possible to have the dreaded error, i.e.

exceptions.RuntimeError Shouldn't load state for 0x01254260 when the connection is closed

That error would not be connected to _v volatile attributes, as they are skipped when storing and are therefor not present when loading. The error has to do with a closed ZODB database connection instead, for whatever reason.

I usually get this kind of error when I store a reference to a persistent object in a non persistent attribute, like a dictionary definied at module level, and then try to access it from a different thread...

Yes, you should not store persistent attribute references outside of the ZODB object tree. Store paths instead, then resolve the path after retrieving it in whatever thread you are in. -- Martijn Pieters