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Date: Sat, 18 Jun 2011 17:19:47 +0000 (UTC)
From: "Mike Matrigali (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
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Subject: [jira] [Created] (DERBY-5284) A derby crash at exactly right time
 during a btree split can cause a corrupt db which can not be booted.
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A derby crash at exactly right time during a btree split can cause a corrupt db which can not be booted.
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                 Key: DERBY-5284
                 URL: https://issues.apache.org/jira/browse/DERBY-5284
             Project: Derby
          Issue Type: Bug
          Components: Store
    Affects Versions: 10.8.1.2, 10.7.1.1, 10.6.1.0, 10.5.3.0, 10.4.2.0, 10.3.3.0, 10.2.2.0, 10.1.3.1
            Reporter: Mike Matrigali
            Assignee: Mike Matrigali


A derby crash at exactly wrong time during a btree split can cause a corrupt db which can not be booted.

A problem in the split code and exact wrong timing of a crash can leave the database in as state 
where undo of purge operations corrupts index pages during redo and can cause recovery boot
to never succeed and thus the database never to be booted.  At hight level what happens is that
a purge happens on a page and before it commits another transactions uses the space of the
purge to do an insert and then commits, then the system crashes before the purging transactions
gets a chance to commit.  During undo the purge expects there to be space to undo the purge
but there is not, and it corrupts the page in various ways depending on the size and placement
of the inserts.  The error that actually returns to user varies from sane to insane as the problem
is actually noticed after the corruption occurs rather than during the undo.


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