Re: Decyphering LMT space bitmap

I think you'll find that generally the initial amount of file allocated is 64K (including the two header blocks) - the fact that you noted the bitmap was in the "next 6 blocks" suggests you were using an 8K block size.

The actual space allocated at file creation time is dependent on the file size, block size, and extent size.

If you have a very small block size, very small extents, and extremely large files then Oracle may allocate an extra 64K (and I guess further multiples of 64K if necessary).

If you create a file that is extremely small, then Oracle can allocate a single block for the bitmap and, if the file then grows, further sections of bitmap may be allocated in the middle of the file.

I have yet to find out what the typical behaviour is for a tablespace with a 32K block. I would guess that the total file header would be 128K rather than 64K - 2 blocks for the general file header, 2 blocks for the bitmap. Could anyone confirm that, thanks ?

Jonathan Lewis
http://www.jlcomp.demon.co.uk

Host to The Co-Operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html

Author of:
Practical Oracle 8i: Building Efficient Databases

-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 08 April 2002 22:55

|
|The bitmap itself is stored in 6 blocks after that , blocks 3 thru 8.
Each of the bit tracks four extents represented by an F (hex for 15).
|0000000000000000 0000000000000000 0000000000000000 00000000000000000
|

{further details cut}
|
|When I did my test and I had raised the question at that time that
the max data that can be stored is 129024 * 6 (blocks) = 774144 extents and if the extent size for argument is 1K then the max size the bitmap can track is 774144K or 7M data file. I have not found an answer yet.
|

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Author: Jonathan Lewis
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