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From Mike Matrigali <mikem_...@sbcglobal.net>
Subject Re: Discussion of how to map the recovery time into Xmb of log --Checkpoint issue
Date Wed, 01 Feb 2006 19:20:41 GMT
I think this is the right path, though would need more details:
o does boot mean first time boot for each db?
o how to determine "this machine"
o and the total time to run such a test.

There are some very quick and useful tests that would be fine to
add to the default system and do one time per database    Measureing
how long to do a commit and how long to do a single database read from
disk would be fine.  Seems like
just these 2 numbers could be used to come up with a very good
default estimate of log recovery time per log record.  Then as you
propose the actual estimate can be improved by meauring real
recovery time in the future.

I am not convinced of the need for the bigger test, but if the default
is not to run it automatically and it is your "itch" to have such
a configuration option then I would not oppose.  I do see great value
in coming up with a very good default estimate of recovery time estimate
based on outstanding number of log records.  And
I even envision
a framework in the future where derby would schedule other non-essential
background tasks that have been discussed in the

On a different track I am still unclear on the checkpoint dirty page
lru list.  Rather than talk about implementation details, I would
like to understand the problem you are trying to solve.  For instance
I well understand the goal to configure checkpoints such that they
map to user understandable concept of the tradeoff of current runtime
performance vs. how long am I willing to wait the next time I boot
the database after a crash.

What is the other problem you are looking at.

Raymond Raymond wrote:

> Mike,
>  Last time we discussed about how to map the recovery time into Xmb of log.
> I have been thinking on it recently and have a proposal.
>  How about when the very first time derby boots (not every time) on a
> certain
> machine, we let the user to chose whether he (or she) want to do some
> statistic
> collection about the system performance. If he (or she) want to do,
> derby runs
> some test, if not, derby doesn't run test. Later, just as what you said,
> we let derby
> collect information every time it does recovery to refine the former
> information.
>   Thanks.
> Raymond
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