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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5691) Document that Write Caching must be disabled to avoid possible database corruption
Date Mon, 07 May 2012 14:12:48 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5691?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13269637#comment-13269637
] 

Knut Anders Hatlen commented on DERBY-5691:
-------------------------------------------

The patch looks fine to me (though I'm not familiar with all the causes of corruption listed
there).

Nit: Third bullet in the Maintaining database integrity topic should have a verb in the imperative
form to match the other bullets. For example:

To avoid database corruption, you can do the following:
(...)
* Do not enable runtime compression of files on disk, as synchronization may fail on some
platforms if the disk runs out of space.

I'm not sure exactly how that problem is specific to runtime compression, as I would also
expect writes to uncompressed files to fail if the disk is full. Is the problem that these
failures are not reported by the operating system and go undetected?
                
> Document that  Write Caching  must be disabled to avoid possible database corruption
> ------------------------------------------------------------------------------------
>
>                 Key: DERBY-5691
>                 URL: https://issues.apache.org/jira/browse/DERBY-5691
>             Project: Derby
>          Issue Type: Improvement
>          Components: Documentation
>         Environment: Microsoft Windows
>            Reporter: Stan Bradbury
>            Assignee: Kim Haase
>              Labels: Write_caching
>         Attachments: DERBY-5691-2.diff, DERBY-5691-2.stat, DERBY-5691-2.zip, DERBY-5691.diff,
DERBY-5691.stat, DERBY-5691.zip
>
>
> Suggestion that we document a recommendation that Windows Write Caching be disabled on
machines using Derby.
> The following article warns about Write Caching on Windows as a possbile source of database
corruption:
>      http://support.microsoft.com/kb/281672
> It is possible that this could be the cause of some unexplained Derby corruptions identified
after power failure of other system interupt.
> Links explaining how to disable Write Caching:
>   Win 2K: http://support.microsoft.com/kb/259716
>    Win 2008: http://support.microsoft.com/kb/324805
> From the Windows 2008 article:
> With some third-party programs, disk write caching has to be turned on or off. Additionally,
turning disk write caching on may increase operating system performance; however, it may also
result in the loss of information if a power failure, equipment failure, or software failure
occurs. This article describes how to turn disk write caching on or off.

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