Re: SIEBEL PERFORMANCE RBO to CBO

Hi,    

  The mutex stuff was discussed on this forum last year   http://www.freelists.org/archives/oracle-l/04-2006/msg01150.html    

  Thanks
  Fairlie

LS Cheng <exriscer_at_gmail.com> wrote:
  Not sure what does mutex do, if someone can explain...

I have seen a place where _kks_use_mutex_pin was set to FALSE to reduce compilation time because 100% of application was written in PL/SQL packages and compiling was a nightmare for them after moving from 9i to 10g, compilation elapsed time contention was around 400% higher due to library cache latching. It was z/OS.

  On 2/5/07, Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk> wrote: Idle thought about HP-UX being the only case where you see CURSOR: PIN S WAIT ON X

I believe the HP chip does not have a compare and swap operation - which Oracle uses for sharable read latches on most platforms. I would guess that the mutex mechanism uses the same chip feature. Presumably the CAS emulation that Oracle does on HP-UX works okay for sharable latches, but has a greater impact on the visibility of mutex operations.

Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com

Author: Cost Based Oracle: Fundamentals
http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html

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

• Original Message ----- >
  > From: "Milen Kulev" <makulev_at_gmx.net>
  > Subject: RE: 10Gr2 and Library Cache Lock Waits
  > Date: Sun, 4 Feb 2007 12:13:49 +0100
  >
  > Ian,
  > What waits events (from v$session_wait) do you get ?
  > If it is "CURSOR: PIN S WAIT ON X" you can try
  > _kks_use_mutex_pin = FALSE.
  > I have several databases , that are running since years well, but after 10g
  > upgrade
  > I have got many "CURSOR: PIN S WAIT ON X".
  > Perhaps it is a coinsidence, but all the databases that are experiencing this
  > problem are
  > Runnung on HPUX. Perhaps this problem has something to do with mutexes
  > implementation
  > On HPUX.
  >
  

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          Fairlie Rego
Senior Oracle Consultant
  http://www.linkedin.com/in/fairlierego
  
  http://el-caro.blogspot.com/
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