Mailing-List: contact derby-user-help@db.apache.org; run by ezmlm
Precedence: bulk
Reply-To: "Derby Discussion" <derby-user@db.apache.org>
Received-SPF: neutral (nike.apache.org: local policy)
MIME-Version: 1.0
Date: Fri, 9 Apr 2010 14:40:54 +1000
Message-ID: <g2n1c4bf5541004082140r188fbe40v410c00515974d07a@mail.gmail.com>
Subject: Copying an idle derby database that is currently open
From: David Sitsky <sits@nuix.com>
To: derby-user@db.apache.org
Content-Type: text/plain; charset=UTF-8

Hi all,

I know this scenario is not recommended, but a couple of our customers
had accidentally copied some Derby databases which were still opened
by a program, however they claim the program had been idle for quite
some time, so there should not have been any active transactions.

I am curious to understand if this is true, is it still possible for
database corruption to occur in the copied versions?  If so, why?  I
can only guess Derby might be doing some background maintenance tasks
(for example, a checkpoint?), and that somehow copying the files
produced inconsistencies since files were changing as they were being
copied, but I am only guessing.

I wish we had the option (at least under Windows) to set the files
open by Derby to be opened "exclusively", so that nobody can even open
them for reading (and thus copy them).  I guess if you "freeze" the
database, you'd have to remove these exclusive locks until the
database is thawed.  A shame we can't do this in Java, or does NIO2
provide this?

-- 
Cheers,
David

Nuix Pty Ltd
Suite 79, 89 Jones St, Ultimo NSW 2007, Australia    Ph: +61 2 9280 0699
Web: http://www.nuix.com                            Fax: +61 2 9212 6902