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Date: Mon, 22 Aug 2005 12:46:35 -0700
From: Mike Matrigali <mikem_app@sbcglobal.net>
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To: Derby Development <derby-dev@db.apache.org>
Subject: Re: Can anyone give me some suggestions?
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Ok, just to be clear Derby checkpoints are already asynchronous.
The one synchrounous point is that while a page is being written
no update that exact page can be happening.
Updates to all other pages in the
database may be going on concurrently with this operation.  So unless
you are worried about concurrency on the single page, I believe
Derby checkpoints already do what you describe.

In the case of Derby the list is the numerical order list of buffers
in the cache, and is always traversed in order.  The checkpoint is
done by a background thread asynchronous to other user threads.

Raymond Raymond wrote:
> 
> 
>> From: Mike Matrigali <mikem_app@sbcglobal.net>
>> Reply-To: "Derby Development" <derby-dev@db.apache.org>
>>
>> Could you define "fuzzy" checkpoint or site what update interference
>> you are trying to avoid.
>>
> 
> Fuzzy checkpointing means checkpoints are asynchronous and occur ant the
> same time as new database updates are being made. The general actions
> in a fuzzy checkpoint are:
> 1. Force log buffer to disk from memory.
> 2. To check if there are any buffer still on the checkpoint list form 
> the previous checkpoint.
>    If there are any, then write them out to disk.(the list is supposed 
> to be empty under
>    some control).
> 3. All dirty buffers will be listed in the current checkpoint list.
> 4. Gather other useful information.
> Once these actions have done, the remainder of the checkpoint can also 
> proceed in
> parallel with future database updates. e.t.: a write process will 
> examine the checkpoint
> list periodically, write some of the buffers on the list to disk and 
> remove thme from the
> list.Under some controls, it is supposed that the list will be empty 
> just befor the next
> checkpoint is taken.
> 
> Those are just the general processes of fuzzy checkpointing. I think we 
> can use some
> technic to make it works more efficient. That is what I am trying to 
> do.^_^.
> Anyone has some ideas about that?
> 
> 
> 
> 
> Raymond
> 
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