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From "Kim Haase (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4525) Document the in-memory storage back end
Date Tue, 09 Mar 2010 14:58:27 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4525?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12843070#action_12843070

Kim Haase commented on DERBY-4525:

I have a couple of questions -- first, about the list of topics above: What is "the new 'drop'
JDBC connection URL attribute"? I cannot find it in either DERBY-646 or http://wiki.apache.org/db-derby/InMemoryBackEndPrimer.

Also, I have been going through the Developer's Guide (http://db.apache.org/derby/docs/dev/devguide/)
checking for topics that need to have information about the in-memory back end added. I think
something should be said in "Derby system" and some of its subtopics. "One Derby instance
for each Java Virtual Machine" (http://db.apache.org/derby/docs/dev/devguide/cdevdvlp96597.html)
has a link to "Double-booting system behavior" (http://db.apache.org/derby/docs/dev/devguide/cdevdvlp20458.html).
This second topic seems to be entirely obsolete, since it describes problems that can happen
with a JVM earlier than 1.4.2, and Derby no longer supports such JVMs. Only the very last
paragraph, about using the Network Server if you want more than one Derby instance to be able
to access a database, is still current. Would it make sense to remove this topic from the
manual and move this last paragraph to the topic "One Derby instance for each Java Virtual

> Document the in-memory storage back end
> ---------------------------------------
>                 Key: DERBY-4525
>                 URL: https://issues.apache.org/jira/browse/DERBY-4525
>             Project: Derby
>          Issue Type: Task
>          Components: Documentation
>    Affects Versions:
>            Reporter: Kristian Waagan
>            Assignee: Kim Haase
>             Fix For:
> The in-memory back end isn't considered experimental anymore, we have to 
> write user documentation for the feature(s).
> I'm not  sure how it should be structured, and where the content should be added.
> Just as a rough cut, here are a few possible topics (I'm not sure if all should be included
or not):
> - documenting the new protocol name ('memory')
> - documenting the new 'drop' JDBC connection URL attribute
> - describing the limitations of the feature (all your data will be lost if..., how to
use it with the client driver and the data sources)
> - "advanced use" (pull dbs on disk into memory, backup in-memory dbs to disk)
> - tuning tips (there are some issues with extreme page cache sizes, maybe the existing
content on page size is valid)
> - known problems (nothing concrete here yet, but we have one inquiry about disappearing
databases - the current theory is that different class loaders are used)
> Some more information is available at http://wiki.apache.org/db-derby/InMemoryBackEndPrimer

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