Hi Scott,

how can you calculate the disk usage of compressed tables for example ?
It depends on data types used, fillfactor, table content (removed
trailing blanks), page size and many more factors. There can be (imho)
no accurate formula I'm afraid.

Jürgen




-------- Original-Nachricht --------
Betreff: [Info-Ingres] How to calculate tables' spaces acurately in Ingres
Datum: Tue, 14 Jul 2009 08:16:01 -0700 (PDT)
Von: Scott <lius (AT) algonquincollege (DOT) com>
Antwort an: Ingres and related product discussion forum
<info-ingres (AT) kettleriverconsulting (DOT) com>
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An: info-ingres (AT) kettleriverconsulting (DOT) com
Newsgruppen: comp.databases.ingres



Hello Folks,

Does anyone have an accurate way to calculate the amount of disk
spaces needed for tables ?

I followed up the method in the section of calculating disk space
from Database Administrator's Guide to do the calculation. It seems
the calculations are not accuate especialy for BTREE struction in our
database(the results of calculations for HEAP are OK). I could get the
pages used by a table at present from iitables and compared them with
the pages required for this table from my calculations, if there were
more than 20% wasted, I reclaimed them by modify <table> to statement,
which should reclaim the lost spaces due to many deletions of this
table. I compared the pages again after modification and found that
there were the same percent of differences. This make me think the
way of calculation is not accurate. Can anyone shed a light on my
issue and have a better and an accurate way to calculate the amount of
disk spaces needed for tables in Ingres.

Thanks,

Scott Liu

Data Analyst
Algonquin College
Ottawa, Canada
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