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From Oystein Grovlen - Sun Norway <Oystein.Grov...@Sun.COM>
Subject Re: High throughput, min durability - tuning
Date Fri, 19 May 2006 13:04:12 GMT
Ashwin Jayaprakash wrote:
> Hello,
> I'm posting several questions about Perf tuning. I'd be grateful if 
> people can provide me with answers.
> 
> I'm using Derby as an Embedded Database for a prototype application, 
> where Derby is used to run queries on a small set of Rows, very 
> frequently. Rows are inserted into the Tables at very high rates. The 
> Queries are run on these new Rows and so they are hot, in the Cache. 
> Once the Query is executed on those Rows, they can be discarded. In a 
> sense, I want Derby to function as an in-memory DB, like Oracle TimesTen.

> I've tuned all the documented parameters like PageCacheSize, PageSize 
> and Durability=test. Are there any other ways I can drastically reduce 
> the Commits to the Disk and thereby eliminate Disk IO? Perhaps rewrite a 
> key Class and add that to the "Pre-Classpath" so that the default 
> behaviour can be over-ridden?

I guess your problem may really be that you are not able to reuse the 
pages used by old rows for new rows after the old rows have been 
deleted.  (I assume you delete your old rows.)  If you could reuse 
existing pages for new data, you would never have to replace pages in 
the cache, and hence you would not be dependent on disk IO for 
performance.  (Assuming you combine this with durability=test).

-- 
Øystein

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