(RE): Calculating LIOs
- From: Wolfgang Breitling <breitliw@xxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 13 Aug 2004 10:27:12 -0600
At 10:02 AM 8/13/2004, you wrote:
>Excellent post mark. However, I have the following
>1 table query that does the following
>select col1, col2
>from table
>where primary_key = <value>
>The table has
>56 rows
>1 MB size. 128 blocks(so 8192 blocksize)
>My 10046 trace shows a full table scan with 63 logical IOs. Roughly half
>the number of blocks. Anyone know why? Looks like I am reading two blocks
>per LIO.
>I figure my number of blocks and bytes in the table by doing the following
>select blocks,bytes
>from dba_segments
>where segment_name = <table>
That's the allocated size. To get the number of blocks the table is
actually occupying, or has ever occupied (HWM), use gather_table_stats and
look at the dba_tables.blocks column, or use the dbms_space procedure.
Regards
Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com
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