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From "Kurt Huwig (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-2836) Documentation of derby.storage.pageSize should mention that the default is dynamic
Date Sun, 17 Jun 2007 12:10:25 GMT
Documentation of derby.storage.pageSize should mention that the default is dynamic
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                 Key: DERBY-2836
                 URL: https://issues.apache.org/jira/browse/DERBY-2836
             Project: Derby
          Issue Type: Improvement
          Components: Documentation
    Affects Versions: 10.2.2.0
            Reporter: Kurt Huwig


The documention of derby.storage.pageSize at docs/html/tuning/rtunproper40688.html says:

  Default

  4096 bytes.

But this page docs/html/tuning/ctunperf816059.html hints, that this default is not necessarily
the one to be used:

"Derby autotunes the database pagesize. If you have long columns, the default pagesize for
the table is set to 32K. Otherwise, the default is 4K."

Also the documentation of derby.storage.pageCacheSize at docs/html/tuning/rtunproper81359.html
does not mention this:

"When increasing the size of the page cache, you typically have to allow more memory for the
Java heap when starting the embedding application (taking into consideration, of course, the
memory needs of the embedding application as well). For example, using the default page size
of 4K, a page cache size of 2000 pages will require at least 8 MB of memory (and probably
more, given the overhead)."

We had one machine crashing, because we expected the page size to be the default of 4096.
After 2 hours of testing, I found out that for my particular example, the page size is set
to 32K. So having a note added would have at least saved me some time and hassle.

I recommend to add the sentence

"Derby autotunes the database pagesize. If you have long columns, the default pagesize for
the table is set to 32K. Otherwise, the default is 4K."

to both the documentation of derby.storage.pageSize and derby.storage.pageCacheSize


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