Re: LMT and what is the Bitmap Header Size?

Rajesh.RaoŁ¬
  hi, you can dump the file header and look at its contents, it can be easily found out.

 2002-08-08 10:36:00 You wrote:
>I have been struggling to find the right answer to the question: What is
>the bitmap header size for a uniform extents LMT? 64K, 1 block, 2
>blocks????
>
>I find one note on Metalink (Note: 111666.1) that says its 64K .
>
>Mr.Jonathan Lewis says " A quirky little detail about bitmap sizes also
>came up recently on the Oracle-L mailing list. If you define a very small
>tablespace - in this context 'very small' means something between 5 blocks
>and '64K plus one extent' then Oracle will give you a bitmap of just one
>block - which still allows you to grow the file quite comfortably, of
>course."
>
>Then another example on Metalink (Note: 109630.1) which goes:
>
> SQL> create tablespace mult
> 2 datafile
> '/oracle2/OFA_base/u02/oradata/V816/mult1.dbf'
> size 100k,
> 3
> '/oracle2/OFA_base/u02/oradata/V816/mult2.dbf'
> size 100k
> 4 extent management local uniform size 50K;
>
> Tablespace created.
>
> SQL> select
> tablespace_name,file_id,block_id,blocks
> 2 from dba_free_space
> 3 where tablespace_name='MULT' ;
>
> TABLESPACE_NAME FILE_ID
> BLOCK_ID BLOCKS
> ------------------------------ ----------
> ---------- ----------
> MULT 15
> 4 25
> MULT 16
> 4 25
>
> BLOCK_ID=4 : In an ordinary datafile, the
> first block where to store data is
> block 2. Therefore, two more
> blocks are reserved for the header
> bitmap of the locally managed
> datafile.
> BLOCKS=25 : The datafile has a size of 100K
> which equals 50 blocks in this
> database =>
> There are only 25 blocks (local
> uniform size 50K)left for data
> starting at block n°4, then 22
> blocks are unused.
>
> => Header bitmap = 2 blocks for each datafile
>
>
>
>
>Moi Confused. Whats the definite word on this? Should be something like if
>the datafile size is x, then its n, else its some other number.
>
>Thanks
>Raj
>
>
>
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>--
>Author:
> INET: Rajesh.Rao_at_jpmchase.com
>
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Good luck!

            chaos
            chaospku_at_163.net

zhu chao
DBA of Eachnet.com
86-021-32174588-667

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Author: chaos
  INET: chaospku_at_163.net

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