Hi Bryan,
thanks for responding :-)
Certainly we have a lot of churn in 2 tables due to periodic updates
which requires the compression.
We find that performance drops significantly (x10) around 1.5 months and
running the full compression, which rebuilds the indexes, makes a
dramatic improvement in performance.
We did try to run the compression online but found that some existing
compiled statements retained a reference to pages in the pre-compressed
table resulting in exception whenever they were excecuted. Since then
we have had to perform the compression offline resulting in downtime.
Jon
On 10/03/2010 16:52, Bryan Pendleton wrote:
Does anybody have experience of running statistics or compression
which they can share?
In my production Derby app, which has run 24x7 for over 4 years, I have
a few tables which I need to compress, approximately every 6 months.
I have not found it necessary to update statistics on my tables.
However, my tables are small and don't change very rapidly, which
is I think the primary reason that I don't need to compress them or
recompute their statistics very often.
I think that if you have highly volatile tables, the need for compression
and statistics is more substantial.
I think you should set up a mechanism to monitor the performance of your
most important transactions, and you should keep an eye on it, and you
should also periodically run SYSCS_DIAG.SYSCS_SPACE_TABLE, etc., and keep
an eye on those values, and, over time, you will probably develop an
intuition about what level of performance degration justifies doing a
statistics or compression pass.
thanks,
bryan
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