> I have big growing tables has default PCT_USED 40%, But we delete data
some
> times one year or 2yrs data. What is optimum value for this parameter?? I
> may consider my database is oltp. So how can decide a correct value for
> this???
PCT_USED might not have any effect for you at all.
If you keep inserting rows by date, the blocks will fill with rows where the
date is the same for every row in the block, or close. Then if the only
time you delete is when you delete an entire year's worth of data, entire
blocks will become empty. That's going to cause them to go on the free list
no matter what you set PCT_USED to.
As the other reply implied, your main concern may be tables where, after the
mass deletes, there are many blocks below the high water mark that are
completely empty. This would take up a little disk space until they are
filled, but the main concern would be that full table scans would take as
long after the deletes as before, due to the need to read all blocks up to
the high water mark (empty or full). So if that is a concern you could
reorg the table.
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--
Author: Greg Moore
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