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Home -> Community -> Mailing Lists -> Oracle-L -> Re: latch wait - cache buffer chain
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
224-405-4079
genegurevich_at_disc
overfinancial.com
Sent by: To
oracle-l-bounce_at_f oracle-l_at_freelists.org
reelists.org cc
frits.hoogland_at_gmail.com, "goran
bogdanovic" <goran00_at_gmail.com>
10/24/2006 05:01 Subject
PM Re: latch wait - cache buffer chain
Please respond to
genegurevich_at_disc
overfinancial.com
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 that?
thank you
Gene Gurevich
"goran
bogdanovic"
<goran00_at_gmail.co To
m> genegurevich_at_discoverfinancial.com
cc
10/24/2006 03:33 frits.hoogland_at_gmail.com,
PM oracle-l_at_freelists.org
Subject
Re: latch wait - cache buffer chain
take the p1raw from the v$session_wait for waiting session and this is your hladdr in the query you are looking for.
On 10/24/06, Frits Hoogland < frits.hoogland_at_gmail.com> wrote: You should find the hottest child latch yourself, and swap the value of ADDR on line 12 with the value of hladdr of the child latch.
if you execute this query, no rows should come up, because the chance of having an hladdr = 'ADDR' in x$bh is fairly low.
cheers!
frits
On 10/24/06, genegurevich_at_discoverfinancial.com < genegurevich_at_discoverfinancial.com> wrote: He everybody:
I am trying to tune a report which has been running for some time and
has
been timing out since last week.
When I execute that report I see a large number of "latch free" wait
events
with p2 parameter equal to 98.
Based on v$latch that is a cache buffer chain latch. One of the reasons
for this event can be a hot block.
I have found the following query on the metalink to locate a hot block:
1 select /*+ RULE */
2 e.owner ||'.'|| e.segment_name segment_name,
3 e.extent_id extent#,
4 x.dbablk - e.block_id + 1 block#,
5 x.tch,
6 l.child#
7 from
8 sys.v$latch_children l,
9 sys.x$bh x,
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 -116* order by x.tch desc
but it did not return anything. Is there anything else I need to look at
related to this latch?
Thanks for any insight
thank you
Gene Gurevich
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Received on Tue Oct 24 2006 - 17:20:47 CDT
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