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From Enrique Rodriguez <enriqu...@gmail.com>
Subject Re: Summer of Code Application
Date Tue, 14 Jun 2005 00:07:19 GMT
Alex Karasulu wrote:
> Enrique Rodriguez wrote:
> 
>> Alex Karasulu wrote:
>> > ...
>>
>>> 2). More backend partition types as noted above by Enrique.
>>> BTW the Prevayler based in memory backend will save major disk IO 
>>> down the line when used to replace the system backend partition.  All 
>>> major subsystems that will be made more robust after subentries are 
>>> implemented will most likely use the system partition to store 
>>> persistent information.  Prevayler from my understanding puts an 
>>> entire db into memory loading it on startup.   On shutdown changes 
>>> are persisted or synch operations can be made intermittently ...
>>
>>
>>
>> Just want to correct a common misconception about Prevayler, since 
>> I've done a couple impl's with it.  Prevayler transactions (more like 
>> "operations," not to be confused with formal J2EE transactions) ARE 
>> immediately persisted to disk.  It's the entire store, which yes is in 
>> memory, that can be configured to periodically full-synch to disk, 
>> generally 24hrs.  Upon crash or other restart scenario the 
>> transactions can be replayed against the last full-synch, ensuring no 
>> loss of data.
> 
> 
> 
> Thanks for the clarification Enrique.  I have never used Prevayler but 
> have looked at it's documentation thanks to your references.  It sounds 
> like a great candidate.
> Does it use HOWL for its transaction log?

Nope.  You write "transactions" using the Command pattern and the state 
of the command object is serialized to disk using JDK object 
serialization.  There's an option to serialize with XML, too.

-enrique

> 
> Alex
> 
> 


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