RE: [QUAR] Re: latch wait - cache buffer chain

  • From: genegurevich@xxxxxxxxxxxxxxxxxxxxx
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Wed, 25 Oct 2006 09:29:51 -0500

Mark, it is Oracle 9204. I'll look into the outlines

thank you

Gene Gurevich

             "Bobak, Mark"                                                 
   >                                                To 
             Sent by:                  <genegurevich@xxxxxxxxxxxxxxxxxxxxx 
             oracle-l-bounce@f         >, <oracle-l@xxxxxxxxxxxxx>         
             10/24/2006 06:15          RE: [QUAR] Re: latch wait - cache   
             PM                        buffer chain                        
             Please respond to                                             

What version of Oracle?  In 10g, there are SQL Profiles.  In previous
versions, stored of them may do the trick.

Mark J. Bobak
Senior Oracle Architect
ProQuest Information & Learning

There is nothing so useless as doing efficiently that which shouldn't be
done at all.  -Peter F. Drucker, 1909-2005

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of
Sent: Tuesday, October 24, 2006 6:21 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: [QUAR] Re: latch wait - cache buffer chain
Importance: Low

Well,  I have executed the same SQL without the index (supressed it by
adding a +0 to a where clause) and it completed in 32 minutes. Still
nothing to write home about  , but better than it was. However the
report is created by a reporting tool and I can't manipulate the SQL. Is
there a way to rebuild that index or change some parameters based on my
findings so that it does not slow down my SQL?

Thanks for any input

thank you

Gene Gurevich
Oracle Engineering



             Sent by:
             oracle-l-bounce@f         oracle-l@xxxxxxxxxxxxx

                                       frits.hoogland@xxxxxxxxx, "goran

                                       bogdanovic" <goran00@xxxxxxxxx>

             10/24/2006 05:01
             PM                        Re: latch wait - cache buffer

             Please respond to



Thank you. Goran and Fritz.

I have now identified an index with a number of "hot" extents.  I
noticed that all the extents in the output of my SQL have the same child
latch #. I am not sure whether this is OK.  I am now trying to rerun my
SQL without the index that was on the hot list to see if that helps.
This index is parallelized and the SQL is executed with 8 readers and 8
writers. Should I change the value of freelist of my index based on

thank you

Gene Gurevich


             10/24/2006 03:33          frits.hoogland@xxxxxxxxx,
             PM                        oracle-l@xxxxxxxxxxxxx

                                       Re: latch wait - cache buffer

take the p1raw from the v$session_wait for waiting session and this is
your hladdr in the query you are looking for.

On 10/24/06, Frits Hoogland < frits.hoogland@xxxxxxxxx> wrote:
  You should find the hottest child latch yourself, and swap the value
  ADDR on line 12 with the value of  hladdr of the child latch.

  if you execute this query, no rows should come up, because the chance
  having an hladdr = 'ADDR' in x$bh is fairly low.



  On 10/24/06, genegurevich@xxxxxxxxxxxxxxxxxxxxx <
  genegurevich@xxxxxxxxxxxxxxxxxxxxx> wrote:
   He everybody:

   I am trying to tune a report which has been running for some time and
   been timing out since last week.
   When I execute that report I see a large number of "latch free" wait
   with p2 parameter equal to 98.
   Based on v$latch that is a cache buffer chain latch.  One of the

   for this event can be a hot block.
   I have found the following query on the metalink to locate a hot
     1  select /*+ RULE */
     2    e.owner ||'.'|| e.segment_name  segment_name,
     3    e.extent_id  extent#,
     4    x.dbablk - e.block_id + 1  block#,
     5    x.tch,
     6    l.child#
     7  from
     8    sys.v$latch_children  l,
     9    sys.x$bh  x,
   10    sys.dba_extents  e
   11  where
   12    x.hladdr  = 'ADDR' and
   13    e.file_id = x.file# and
   14    x.hladdr = l.addr and
   15    x.dbablk between e.block_id and e.block_id + e.blocks -1
   16*   order by x.tch desc

   but it did not return anything. Is there anything else I need to look

   related to this latch?

   Thanks for any insight

   thank you

   Gene Gurevich






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