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From Dag Wanvik <dag.wan...@oracle.com>
Subject Re: Stopping network server & cold backup
Date Fri, 21 Sep 2012 20:23:29 GMT

On 21.09.2012 18:54, Mo Maison wrote:
> Thank you for this tip.
> I do not feel confident with whole DB freeze, as I do not know DB size,
> thus I can't estimate the time required to copy files. Also I fear
> something
> goes wrong and UNFREEZE is never called.
> In case, is restarting the Derby server sufficient to "forget" this
> frozen state ?


> Regarding my initial question : is there somewhere a file to watch
> that indicates that server is fully shutdown ?
> There is probably a kind of lock file that indicates that a DB is
> being used ?

<dbdir>/db.lock is created when a database is booted by a VM, to avoid
several VMs trying to boot the same database.
The derby *server* (engine) can open several databases. By by shutting
down a database
the corresponding lock file is removed, but the server can still be
alive waiting for connections. Presently, I think the only way to portably
check if the server is still alive is to try to connect to its port.


> Watching server process in /proc would be ugly and not portable.

> M. Maison
> Le 31/07/2012 22:59, José Ventura a écrit :
>> I'm using the tips in this page to achieve a similar goal:
>> http://db.apache.org/derby/docs/10.6/adminguide/cadminhubbkup75469.html
>> Basically, instead of shutting down the server, you use a command to
>> freeze the DB, then copy the files, then unfreeze the DB. The freeze
>> call will block until it is safe to copy the files.
>> On Tue, Jul 31, 2012 at 5:49 PM, Mo Maison <momaison@yahoo.fr
>> <mailto:momaison@yahoo.fr>> wrote:
>>     Hello Derby users,
>>     I encounter sometimes a problem during cold backups :
>>     Derby is launched as a server (listening localhost only ) ;
>>     I stop the network server with standard command :
>>       java -cp ... \
>>       org.apache.derby.drda.NetworkServerControl shutdown \
>>       -h localhost -p 1527
>>     Right after command has returned, I perform a tar of the
>>     database files.
>>     However, I have observed that, on a slow filesystem, somes
>>     files get deleted while tar is reading them. Which let me think
>>     that server is not fully stopped when process returns
>>     (and thus backup may be corrupted).
>>     Is that expected ?
>>     How can I be sure that everything is quiescent before performing
>>     the cold backup ?
>>     I use Derby 10.6.2 on 32 bits Linux.
>>     Thank you for your advices,
>>      M. Maison

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