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From Bryan Pendleton <bpendleton.de...@gmail.com>
Subject Re: Page cache sizing
Date Fri, 07 Jul 2017 02:59:40 GMT
how does derby.storage.pageCacheSize parameter (https://db.apache.org/derby/
> docs/10.13/ref/rrefproper81359.html) work with database that has multiple
> page sizes--tables with default 4096 bytes and tables with long/blob of
> 32768 byte pages?
>
>
Hi Peter,

I'm not 100% sure how this works; I think you should run some experiments.

Here's what I *think* the behavior is:
1) The page cache is sized in 4K pages, so if you set pageCacheSize=1024,
you get 4 meg of page cache memory
2) Tables with 4K pages simply use the cache as you expect.
3) Tables with 32K pages chew up 8 cache "pages" at a time, each 32K chunk
of page cache holding 1 32K page from that large-page table.

Some stuff I found while searching around, which might give you some ideas
for experiments you could run:

http://apache-database.10148.n7.nabble.com/out-of-memory-when-writing-blobs-td100948.html

and

https://issues.apache.org/jira/browse/DERBY-4537

Sorry I'm not of much more help here.

bryan

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