Re: num of blocks containing table data

On Sat, 13 Jun 1998 22:01:46 GMT, Jurij Modic <jurij.modic_at_mf.sigov.mail.si> wrote:
>On Fri, 12 Jun 1998 10:50:26 GMT, "Jonathan Lewis"
><jonathan_at_jlcomp.demon.co.uk> wrote:
>
>>
>>Why do you want this figure though, since it doesn't appear to be a
>>meaningful number. For instance, if you want the number which is:
>>'the minimum number of blocks which I could recreate the table in'
>>then look at:
>> (average row size + row overhead) x row count.
>
>To me it doesn't appear to be totaly meaningless number. For example,
>if you want to monitor how table's blocks are filled during the life
>of application to verify the correctness of the PCTFREE/PCTUSED
>settings, you could compare the numbers from your formula, from HWM
>and from the occupied block count to decide if it is rational to
>rebuild your table (perhaps with different storage parameters).
>
>Of course, I can estimate (probably with acceptable accuracy) the
>number of occupied blocks, but I was simply surprised to find out that
>there seems to be no method to exactly determine this number in all
>circumstances. At all the various statistics that Oracle is offering
>it realy surprises me that I can not determine such a basic data.

If it's not particularly useful and there are other acceptable determinants, it's not all that basic. The statistics and settings are based on large samplings, so exact determinations suffer from the error of over-precision: like Mr. Spock saying it is exactly 5107.1235 meters to the next town, when you need to know if you should walk or take a spaceship.

For example, you would care more about 50% row-chaining than that you have 432944 free blocks and 453234 used ones.

>
>But to be honest, it is realy only my curiosity.

Nothin' wrong with that! It has helped illustrate that there are so many complexities that simply counting used blocks is not simple, and you shouldn't lose sight of what you really want to know.

>
>>Jonathan Lewis
>
>Regards,
>============================================================
>Jurij Modic Republic of Slovenia
>jurij.modic_at_mf.sigov.mail.si Ministry of Finance
>============================================================
>The above opinions are mine and do not represent any official
>standpoints of my employer

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