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From Knut Anders Hatlen <Knut.Hat...@Sun.COM>
Subject Re: Some questions about derby cache page!
Date Thu, 09 Feb 2006 06:44:13 GMT
Raymond Raymond <raymond_derby@hotmail.com> writes:

> I have some questions about derby cache page, anyone can help me?
> 1. Derby writes out dirty pages through two ways:
>     - A background thread writes out dirty pages based on some
>       algorithm such as LRU.
>     - Checkpointing process writes out all the dirty pages.
>     I want to know after a dirty page has been written out, the
>     page will be discarded? or the status of the page will be set
>     as "clean"?

If a page is written by the checkpoint or background writer, it is
set to clean and kept in the page cache.

You have one more way to write out dirty pages. When a new page is to
be put into the page cache, and the page cache is full, a page has to
be thrown out of the cache. If a clean page cannot be found, a dirty
page will be written and removed from the cache.

> 2. If a cache page has been updated serval times, is there any
>     information can indicate the log instance for every update?
>     or just the last update?

I think you only have information about the last update. You might
have a look at BasePage.updateLastLogInstant() and see if you can make
it keep more information.

-- 
Knut Anders


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