Re: Extent allocation (New DBA Question)

Hi,
When Oracle allocated the initial extent, it searches for contigious blocks + 1 which in this case will be 8. If it cannot find 8 blocks it searches for a greater set than 8 blocks and in this case found 10 contigous blocks and allocated it to the extent. If it had found 13 blocks (req number + 5), it will allocate 8 blocks to the extent and leave the 5 blocks free. If it finds 9, 10,11 or 12 contigous blocks then it allocates all of them to the extent.

You can refer to the Oracle Concepts Manual (Extents, Blocks and Segments Chapter) if you need more detailed information.

Hope this helps.
Regards,

Madhavan
IBM Corporation Webserver Div

>From: "Lindsay Stoddard" <lindsay.stoddard_at_osha-slc.gov>
>Reply-To: ORACLE-L_at_fatcity.com
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>Subject: Extent allocation (New DBA Question)
>Date: Tue, 16 May 2000 12:26:50 -0800
>
>Hi,
>
>I am using the following SELECT statement to obtain space information about
>table objects:
>
>COL Segment_Name FORMAT a25 HEADING "Table Name"
>COL Tablespace_Name FORMAT a10 HEADING "Tablespace"
>COL Bytes FORMAT 99,999,999 HEADING "Bytes"
>COL Blocks FORMAT 9,999,999 HEADING "Blocks"
>COL Extents FORMAT 99,999 HEADING "Extents"
>COL Next_Extent FORMAT 99,999,999 HEADING "Next Extent"
>COL Initial_Extent FORMAT 99,999,999 HEADING "Initial Extent"
>
>SELECT Segment_Name,
> Tablespace_Name,
> Bytes,
> Blocks,
> Extents,
> Initial_Extent,
> Next_Extent
> FROM DBA_SEGMENTS
> WHERE Owner = UPPER('&&owner')
> AND segment_type = 'TABLE'
> ORDER BY Segment_Name;
>
>One of the rows returned from this SELECT is:
>
>Table Name Tablespace Bytes Blocks Extents Initial
>Extent Next Extent
>------------------------- ---------- ----------- ---------- -------
>--------
>------ -----------
>PART_NO USERS 81,920 10 1
>57,344 57,344
>
>The database has a db block size of 8K.
>
>I am wondering why only one extent is being used although the "Bytes" being
>used is more than the "Initial Extent". The initial extent is equal to 7
>blocks at 8K a piece. My thinking is that another extent would have been
>used once the Bytes went over 57,344 and Blocks would be 14. To me, Blocks
>should be 7 or 14 etc. Whats happening?
>
>Thanks to anyone who can help,
>
>Lindsay Stoddard
>ACS - GSG
>
>--
>Author: Lindsay Stoddard
> INET: lindsay.stoddard_at_osha-slc.gov
>
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