RE: db file scattered read

From: Cary Millsap <cary.millsap_at_hotsos.com>
Date: Fri, 14 Mar 2003 11:54:43 -0800
Message-ID: <F001.0056AB61.20030314115443@fatcity.com>

For the answer to your first question, see Jeff Holt's "Predicting Multiblock Read Size" at www.hotsos.com/catalog. Prior to Release 9, the statistic "ela= 1" means that the syscall lasted somewhere between 0.005000 and 0.014999 seconds in duration. Full details forthcoming in <shameless_plug>"Optimizing Oracle Performance"</shameless_plug>, due out in approximately July.  

Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com

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-----Original Message-----

Sent: Friday, March 14, 2003 11:05 AM
To: Multiple recipients of list ORACLE-L  

Here is a part of trace file . I am finding that oracle is trying to read 8 or 3 or 7 blocks at a time . But block numbers are all sequential i.e. it will read 3 blocks starting from 14706 and then 8 blocks starting from 14710 ( 14706+3 ). Why it doesn't read 8 blcoks always it multi_block_read is set to 8 ? Any Idea .

Also what is ela=1 ,does it mean elapsed time is 1 sentisec ?      

WAIT #32: nam='db file scattered read' ela= 0 p1=4 p2=14706 p3=3
WAIT #32: nam='db file scattered read' ela= 1 p1=4 p2=14710 p3=8
WAIT #32: nam='db file scattered read' ela= 2 p1=4 p2=14718 p3=8
WAIT #32: nam='db file scattered read' ela= 0 p1=4 p2=14727 p3=3
WAIT #32: nam='db file scattered read' ela= 0 p1=4 p2=14731 p3=7
WAIT #32: nam='db file scattered read' ela= 1 p1=4 p2=14739 p3=3
WAIT #32: nam='db file scattered read' ela= 1 p1=4 p2=14744 p3=8
WAIT #32: nam='db file scattered read' ela= 1 p1=4 p2=129784 p3=8

 

 

Thanks

-ak

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Author: Cary Millsap
  INET: cary.millsap_at_hotsos.com

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