db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Suresh Thalamati <suresh.thalam...@gmail.com>
Subject Re: Some questions about derby cache page!
Date Fri, 10 Feb 2006 19:12:10 GMT
Hi Raymond,

As Knut mentioned, Only log Instant for the last update on a page is 
maintained, this is needed to make sure log is flushed to that point , 
if page is flushed to the disk.

I am just curious, why would you want to keep track of log instant for 
each update ?

Thanks
-suresht

Knut Anders Hatlen wrote:
> 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.
> 


Mime
View raw message