[jira] Commented: (DERBY-2836) Documentation of derby.storage.pageSize should mention that the default is dynamic

["Laura Stewart (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DERBY-2836?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12518198 ] 

Laura Stewart commented on DERBY-2836:
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Thanks Kurt, this is a good suggestion. I will add the sentence to the two files.

> Documentation of derby.storage.pageSize should mention that the default is dynamic
> ----------------------------------------------------------------------------------
>
>                 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
>            Assignee: Laura Stewart
>
> 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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