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From Mike Matrigali <mikem_...@sbcglobal.net>
Subject Re: how does derby avoid eating up all the system resources if it's used embeddedly
Date Wed, 19 Oct 2005 18:20:43 GMT
My question was in reference to whether derby should schedule additional
background house keeping chores.

With respect to directly executing queries that have been requested by
the application Derby will attempt to use all resources available under
the following restrictions (currently):
     o a single connection will only ever execute within a single thread
       at one time.  So a single user can never take over more than a
       single cpu.
     o There is currently a single background thread to do work like
       reclaim committed deleted space, again currently this can at most
       use a single CPU.

Raymond Raymond wrote:
> Hi, Dear Mike, since you said "Are there any opinions out there on how 
> to determine
> if Derby "is busy"?  " and it is not good for derby to eat up all the 
> system resources,
> I am curiously want to know presently how does derby avoid eating up all 
> the system
> resources if it can't dertermine it's busy or not?
> 
> Thanks.
> 
> Raymond
> 
> 
>> From: Mike Matrigali <mikem_app@sbcglobal.net>
>> Reply-To: "Derby Development" <derby-dev@db.apache.org>
>> To: Derby Development <derby-dev@db.apache.org>
>> Subject: Re: Some idea about checkpoint issue, welcome to give your idea
>> Date: Tue, 11 Oct 2005 10:57:08 -0700
>>
>> Are there any opinions out there on how to determine if
>> Derby "is busy"?  Is there something better than just having
>> a low priority thread  and maybe some query of cpu vs. elapsed
>> time?
>>
>> The first problem is that I don't think there are great tools
>> for this in java.  The second problem is that often Derby is
>> meant to be embedded as part of another application, so we have
>> to be careful not to implement a standard server based approach
>> where it is appropriate for the "server" to use up all resources
>> available (ie. idle time may not really be best used by derby
>> admin processes).
>>
>> I have not come up with a good answer to this problem, there are
>> a number of things derby could do if it knew it had idle time
>> available for it's use.  Best I have come up with is some mode
>> in the system that needs to be set by the application which
>> starts up Derby - either derby try's to limit it's use of idle
>> cycles or it enabled to try and schedule work during idle time.
>>
>> Raymond Raymond wrote:
>>
>> > I have been thinking of the automatic checkpointing issue
>> > recently.I also find someone added another issue about "Use
>> > of idle time for background checkpoint" into the to-do list.
>> > I think we can consider these two issue together. I have
>> > some idea about it.
>> >
>> > Instead of doing checkpoint periodically and trying to tune the
>> > checkpoint interval to achieve best performance, is it possible to
>> > keep the background checkpoint process running to do checkpoint,
>> > and the DBMS can tune the rate of checkpoint depending on the
>> > current system situation,e.g. if the system is busy, derby will
>> > slow down the checkpoint rate and if the system is not busy(idle),
>> > derby will speed up the checkpoint rate.We will update the control
>> > file periodically to let the DBMS know up to where we did checkpoint.
>> > Maybe we can call it 'increamental checkpointing'. In my opinion,
>> > this approach can use the disk IO resources with reason if we can
>> > decide the checkpoint rate reasonablly.
>> >
>> > I would like to discuss this issue with everyone. I am not
>> > sure if this approach is doable or not. If it is doable, I will
>> > have some further questions about how to decide the appropriate
>> > checkpoint rate.
>> >
>> > Thanks.
>> >
>> > Yours, Raymond
>> >
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