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From Stanley Bradbury <Stan.Bradb...@gmail.com>
Subject Re: The size of caches for dataDictionary
Date Tue, 20 Feb 2007 19:19:27 GMT
Yifan wrote:
>
> I have looked into the code for data dictionary. In the source code, 
> there are some caches for tables or columns.
>
> One thing I am a little confused is the size of these caches.
>
> For example, if there is no DDL statement but only DML statement which 
> manipulate on all tables, will the table cache keep all tables in 
> memory or just part of them?
>
> If we do not have enough memory, will table belong to further DML 
> statement being cached or not?
>
>  
>
> Thanks
>
> Yifan
>
The setting of pageCacheSize determines the number of pages that will be 
held in the data cache.  New pages needed to satisfy the DML executed 
will be added to the cache until the pageCacheSize limit is reached.  At 
this point the LRU pages in the cache will be removed to make room for 
newly referenced pages. 

Theoretically, if the pageCacheSize is larger than the size of all the 
tables and indexes in the database , all the the tables could become 
loaded into the cache and remain there until Derby is shutdown.

HTH



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