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From "Kathey Marsden (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5691) Document that Write Caching must be disabled to avoid possible database corruption
Date Tue, 22 May 2012 18:01:43 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5691?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13281123#comment-13281123
] 

Kathey Marsden commented on DERBY-5691:
---------------------------------------

Hi Kim,
I am sorry I missed the change regarding disk full. Disk full in and of itself should not
in itself cause corruption but will prevent boot.  Normally once more disk is added or made
available, Derby should be able to recover.  Of course it is always a good idea to leave plenty
of disk space so you can still run, but not doing so should not corrupt your database.

As Mike said, we had one scenario where we theorized  that runtime file system compression
violated Derby's assumption  that it will only get  out of disk space error when growing the
file.   That was the motivation for the entry and the case where we think corruption could
occur.   

Also, I am going to open up a new issue on the causes of and recovering from a checksum error
which I think will fit well into this new section. 

Thanks for your work on this important issue.



                
> 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
>             Fix For: 10.8.2.3, 10.9.0.0
>
>         Attachments: DERBY-5691-2.diff, DERBY-5691-2.stat, DERBY-5691-2.zip, DERBY-5691-3.diff,
DERBY-5691-3.zip, DERBY-5691-4.diff, DERBY-5691-4.zip, DERBY-5691-5.diff, DERBY-5691-5.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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