[ZODB-Dev] Preventing a folder from being packed

[Shane Hathaway]

Toby Dickenson wrote:
> On Friday 16 May 2003 4:28 am, Shane Hathaway wrote:
> 
>>Echoing Sean's point, at ZC we have lately followed a pattern of using
>>mounted databases because different parts of the object system have
>>different database requirements.  Catalogs, sessions, and Wikis all get
>>mounted for different reasons.  Packing characteristics are only one
>>dimension.
> 
> How do you avoid synchronisation problems across undo when Catalogs are in 
> their own storage?

In theory, we could set some transaction metadata that links 
transactions from multiple databases together.  The undo feature would 
look for the special tag and transparently undo in other databases 
simultaneously.

In practice, we've just ignored undo synchronization issues for now. :-) 
  Seriously, the synchronization tends to not matter much.  The need for 
undo is rare.  Also, catalogs have had minor issues long enough that 
catalogs are now pretty robust in the face of synchronization errors.

Shane