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From Knut Anders Hatlen <knut.hat...@oracle.com>
Subject Re: Reclaiming space from Derby
Date Wed, 08 Sep 2010 15:45:31 GMT
Paul Taylor <paul_t100@fastmail.fm> writes:

> Knut Anders Hatlen wrote:
>> Paul Taylor <paul_t100@fastmail.fm> writes:
>>
>>   
>>> HI, I use derby in embedded mode, I let the user specify a maxmium
>>> size for the derby database files, my program monitors this and if it
>>> goes over the size I use SQL to delete records that are no longer
>>> necessary in the hope of shrinking the database files size, but it
>>> doesn't, how can I force Derby to shrink back down ?
>>>     
>>
>> Hi Paul,
>>
>> The database files won't shrink unless you compress the tables.
>>
>> http://db.apache.org/derby/docs/10.6/ref/rrefaltertablecompress.html
>> http://db.apache.org/derby/docs/10.6/ref/rrefproceduresinplacecompress.html
>>
>> Hope this helps,
>>
>>   
> Thanks guys that does help, the only problem is that it takes an
> exclusive lock on the table and I wanted to run it in the background
> as and when required when other tasks might be going ahead. But can
> probaly work round this.

In the issue tracker there's a request for allowing more concurrent
activity while compressing a table, but there hasn't been any work on it
yet. https://issues.apache.org/jira/browse/DERBY-3974

-- 
Knut Anders

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