Re: [OJB-developers] Single VM Object Cache Consistency?

[Thomas M. <tho...@ho...>]

Hi John,

<snip>

 >
 >
 > I'm working on trying to change things so that
 >
 > a) Each PB has its own private object cache which is transactionally
 > consistent (the cache is flushed on each commit/abort tx.  This behavior
 > is controlled via OJB.properties.


great news !


 >
 > b) Classes can be marked for "VM wide" caching (multiple PBs will share
 > these objects).  These classes must be thread safe and used to hold
 > "read only" data from the database.  This cache is not flushed
 > automatically when tx's commit/abort.
 >


good idea!


 > I've got it coded and I'm testing it out more today.  It is mostly a new
 > cache implementation class - the impact on the rest of the code is
 > actually pretty minimal (and this new behavior can be turned on/off
 > easily).
 >


that's good!


 > However, your comment about the cache providing "uniqueness of
 > persistent Objects across a VM" concerns me.  Clearly with PB local
 > caches, you can have multiple object instances in the VM that have
 > identical database identity.  From what I can tell, I don't see this as
 > a problem, but with your greater experience do you see any problems with
 > the above approach?


I agree with you: if the transaction local caches are flushed on tx
commit I see no problems with this approach.

 > Would this play havoc with the higher layers that
 > I'm not familiar with (odmg or the planned jdo)?
 >


No, should be harmless.

thanks for your efforts!

Thomas


 > Regards,
 >  - John
 >
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