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From Mike Matrigali <mikem_...@sbcglobal.net>
Subject Re: Database size larger than expected
Date Fri, 21 Oct 2011 22:24:06 GMT
There are a number of factors:

1) an "empty" derby database takes up 770k in 10.9.  This is 71 system 
catalogs and indexes on those system catalogs.  Even empty tables still
have inital empty pages allocated and written, in the default they take
at lease 8k each.  Each file in seg0 represents either a table or an
index.  I assume you meant you have a Derby database with 2 tables, so
only 2 of the files in seg0 have data for your tables.  They are likely
the 2 biggest files in seg0.

2) By default the system also reserves empty space in pages for future 
updates.  I think the default in 20% reserved.  There are properties to
override this.

3) Each record has overhead and each field has overhead that is variable.

4) The tables will begin allocating 8 pages at a time when they need
a new empty page.  So worst case could be 7 empty pages at the end.


anthonyri wrote:
> David,
> 
> No indexes I am afraid, should have mentioned that, sorry.
> 
> Anthony
> 
> 
> David Zanter wrote:
>> Do you have Indexes on those Tables?
>>
>>
>> On Fri, Oct 21, 2011 at 5:29 PM, anthonyri <anthony.rich@inbox.com> wrote:
>>
>>> Hi,
>>>
>>> I have a Derby database with two records, the first has 5000 records (of
>>> int, double, double, double, double - so approx 34 bytes per record), the
>>> second has 1000 records (of int, varchar(10), varchar(40) - so approx 102
>>> bytes per record).
>>>
>>> 5000 * 34 = 166k
>>> 1000 * 102 = 100k
>>> Total = 266k (if it was in a text file)
>>>
>>> What I don't understand is why the database (seg0 folder) is 1.2MB?
>>>
>>> I have compacted the database using;
>>>
>>> call SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE('APP', 'mapObject', 1, 1,
>>> 1);
>>> call SYSCS_UTIL.SYSCS_COMPRESS_TABLE('APP', 'MAPOBJECT', 1);
>>>
>>> Any thoughts please?
>>>
>>> Anthony
>>> --
>>> View this message in context:
>>> http://old.nabble.com/Database-size-larger-than-expected-tp32699233p32699233.html
>>> Sent from the Apache Derby Users mailing list archive at Nabble.com.
>>>
>>>
>>
> 


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