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Re: reading the SGA from my own program

Anjo Kolk

2006-08-21

Replies:
 
There are a couple of resaons why this is (was) valid:
1) Overhead
    Sampling the v$SESSION_WAIT once a second is something that can't be done with normal queries (not completely true) and mapping different pointers.
    A join of v$session_wait, v$session and v$sqlarea is rather expensive if you want to find the current sql statement that causes the wait, very cheap with
    direct SGA attach.
2) Information
    Sometimes to get usefull info from V$ or X$ tables, one needs to join  them and even then it becomes not possible. By having access to the SGA
    one can join structures together that can't be done in normal SQL.
3) Geeky stuff
    Really cool to do ;-)
 
Anjo.


 
On 8/21/06, Allen, Brandon <Brandon.Allen@oneneck.com> wrote:
Please forgive my ignorance, but what is the point of this direct SGA access anyway?  Why not just query v$session_event and/or v$session_wait, or the underlying x$ tables?
 
Thanks,
Brandon


From: oracle-l-bounce@freelists.org [mailto: oracle-l-bounce@freelists.org] On Behalf Of Tanel Poder
Sent: Saturday, August 19, 2006 2:30 AM
To: anjo.kolk@oraperf.com
Cc: jeremiah@ora-600.net; 'Oracle Discussion List'
Subject: RE: reading the SGA from my own program
 
Also, if all you're interested in is the current wait state of a session, then there's no real fundamental need to map those SHM segments which do not contain the data you're interested in (as far as I understand).
 
Tanel. 
 
. . . 
 

From: oracle-l-bounce@freelists.org [mailto: oracle-l-bounce@freelists.org] On Behalf Of Jeremiah Wilton
Sent: Saturday, August 19, 2006 05:14
To: 'Oracle Discussion List'
Subject: reading the SGA from my own program

 

I am trying to play around with reading the SGA using my own program, as popularized by Kyle Hailey and Miladin Modrakovic's papers and presentations.  I am confused about where to find x$ksusecst (session wait) and other items in the fixed area.

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