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From David Van Couvering <da...@vancouvering.com>
Subject Issues with open files in Derby
Date Mon, 14 Jun 2010 22:42:35 GMT
I am running a system that is opening a fairly large number of databases
within a single server environment.  The problem is each database is keeping
open a certain number of files, and on some systems is causing failures from
too many open files.

I am trying to work around this by shutting down the database whenever it's
not in use, but my current system regularly scans all databases every five
seconds, and so I'm booting and shutting down the databases constantly.
This is exacerbated by the fact that I have other threads that are also
updating some subset of these databases.

I have tried to deal with this through a central registry that tracks usages
of a database and shuts it down only when it's not in use, but it's been
difficult to get right, and I either end up with leaks or with exceptions
caused by one thread being in the middle of updating a table while another
thread is shutting it down.  The different kinds of exceptions I get are
quite varied and nasty, and involve not only errors caused by shutdown, but
recovery errors when a database was shut down while it was also being
updated.

So, I have a couple of questions for you all:

- Do the number of files held open by a database grow as the number of rows
in a table grows?  Some of these tables will have millions of records.
- Is there any way to tell Derby to close out open files and/or reduce the
number of open files to a minimum?
- Is it a known issue that shutting down a database will corrupt the
database if another thread is updating it?

Thanks,

David

-- 
David W. Van Couvering

http://www.linkedin.com/in/davidvc
http://davidvancouvering.blogspot.com
http://twitter.com/dcouvering

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