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From Knut Anders Hatlen <Knut.Hat...@Sun.COM>
Subject Re: A question about dirty pages.
Date Wed, 01 Mar 2006 08:54:19 GMT
Raymond Raymond <raymond_derby@hotmail.com> writes:

> I have a question needs to be confirmed. Anyone can help me?
>
> In checkpoint, derby checks from the last cached item in the
> holder array to the first one(ref:
> org.apache.derby.impl.services.cache.Clock.java)
> to find dirty pages and write them out.
> A cache page, which is clean before checkpoint starts and is updated
> after checkpoint starts, will have a chance to be written out by the
> current checkpoint process. Am I right?
> For instance, let's assume derby keeps 1000 cache pages. When
> checkpoint starts, it checks from the 1000th cache page to the
> first one. When it goes to check the 800th cache page, the 700th
> cache page is updated. The 700th cache page will be checked later
> and written out as a dirty page( assume it is valid). If the 900th cache
> page is updated when the 800th cache page is checked. The 900th
> cache page will not be written out by the current checkpoint process.
> Am I right?

Yes, your description of the checkpoint process is correct.

-- 
Knut Anders


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