Comments for Latch, mutex and beyond http://andreynikolaev.wordpress.com Yet another look on Oracle latch performance Tue, 12 Feb 2013 14:42:07 +0000 hourly 1 http://wordpress.com/ Comment on Divide and conquer the “true” mutex contention by Reducing “library cache: mutex X” concurrency with dbms_shared_pool.markhot() « Julian Dontcheff's Database Blog http://andreynikolaev.wordpress.com/2011/05/01/divide-and-conquer-the-true-mutex-contention/#comment-591 Tue, 12 Feb 2013 14:42:07 +0000 http://andreynikolaev.wordpress.com/?p=1718#comment-591 [...] PL/SQL packages and procedures, use dbms_shared_pool.markhot() to mark them as hot. As suggested by Andrey Nikolaev, Oracle creates multiple copies of marked objects in the library cache, but frequently uses only [...]

]]> Comment on Strange “db file async I/O submit” wait event by amalendu chakraborty http://andreynikolaev.wordpress.com/2010/07/29/db-file-async-io-submit-wait-event/#comment-578 Tue, 05 Feb 2013 21:29:05 +0000 http://andreynikolaev.wordpress.com/?p=249#comment-578 Thank you for the post. I am also having the same issue , got confused by this event. Oracle should do a better job of documenting their wait events.

]]> Comment on RuOUG2012 by andreynikolaev http://andreynikolaev.wordpress.com/2012/12/10/ruoug2012/#comment-564 Fri, 18 Jan 2013 20:41:36 +0000 http://andreynikolaev.wordpress.com/?p=4694#comment-564 Hello!
This is interesting latch contention case.
Can you additionally describe:
1. Exact Oracle version and patches..
2. Problematic “two SQLs” and their execution plans
3. Run my script
@latch_stats_10g.sql
and send me the results

You can contact me at email Andrey.Nikolaev@rdtex.ru
Best Regards
Andrey

]]> Comment on RuOUG2012 by Tonydba http://andreynikolaev.wordpress.com/2012/12/10/ruoug2012/#comment-563 Thu, 17 Jan 2013 15:51:06 +0000 http://andreynikolaev.wordpress.com/?p=4694#comment-563 Hi Andrey,
Not sure whether it’s a right place to ask you something about latch cache buffer chain contention on an index root block.Since I don’t have your email ID,I am placing my question in the comment section.In my production system(oracle 10.2.0.4) users are complaining slowness when they try to retrive few rows from a tiny table(133 rows in 5 blocks) using “Unique Index Scan”.The index has only 1 block(root,leaf,branches all in one).I could see a severe latch:cbc contention on two SQLs that are executed at very higher rate(250/sec) from multiple users.
NAME HMODE FUNC OBJECT Held Gets Held % Held ms Avg hold ms
————- ——————— ———— ——————————— ———- ———- ——- ———– ———–
f7srmb2gqa245 cache buffers chains exclusive kcbgtcr: kslbegin excl 400011C 105103 101444 10.51 10057.306 .099
f7srmb2gqa245 cache buffers chains exclusive kcbrls: kslbegin 400011C 69188 66923 6.92 6620.600 .099
5cmrd9mq8jnr8 cache buffers chains exclusive kcbgtcr: kslbegin excl 400011C 5773 5503 .58 552.418 .100
5cmrd9mq8jnr8 cache buffers chains exclusive kcbrls: kslbegin 400011C 3438 3260 .34 328.982 .101
f7srmb2gqa245 cache buffers chains shared kcbgtcr: kslbegin excl 400011C 1227 1227 .12 117.412 .096
f7srmb2gqa245 cache buffers chains shared kcbrls: kslbegin 400011C 929 929 .09 88.896 .096

why would a select statement needs an execlusive latch access in this case?

Thanks
Tony

]]> Comment on RuOUG2012 by goryszewskig http://andreynikolaev.wordpress.com/2012/12/10/ruoug2012/#comment-521 Tue, 11 Dec 2012 08:40:34 +0000 http://andreynikolaev.wordpress.com/?p=4694#comment-521 Thank You .

]]> Comment on Spin tales: Part 1. Exclusive latches in Oracle 9.2-11g by Werken met Latches | Vijfhart Weblog http://andreynikolaev.wordpress.com/2011/01/06/spin-tales-part-1-exclusive-latches-in-oracle-9-2-11g/#comment-508 Thu, 22 Nov 2012 09:10:13 +0000 http://andreynikolaev.wordpress.com/?p=421#comment-508 [...] de CPU welke 10-12 miliseconde duurt, is dit ontzettend lang vergeleken bij een latch. Daarom “spint” een latch als deze bezet is. Eigenlijk is dit niets anders dan een loop; een latch “loopt” [...]

]]> Comment on Mutex waits. Part II. “Cursor: Pin S” in Oracle 11.2 _mutex_wait_scheme=0. Steps out of shadow. by Nilesh http://andreynikolaev.wordpress.com/2011/10/25/mutex-waits-part-ii-cursor-pin-s-in-oracle-11-2-_mutex_wait_scheme0-steps-out-of-shadow/#comment-507 Wed, 21 Nov 2012 17:21:11 +0000 http://andreynikolaev.wordpress.com/?p=3137#comment-507 Hi Wenju,

We are facing similar problem in our environment due to mutex X waits. would you able to share the logic/code of your job “to monitor the mutex wait events using v$active_session_history, and if it reaches certain thresholds, then the job would drop the plan baselines or sql profiles associated”

Thanks,
Nilesh

]]> Comment on Divide and conquer the “true” mutex contention by andreynikolaev http://andreynikolaev.wordpress.com/2011/05/01/divide-and-conquer-the-true-mutex-contention/#comment-480 Wed, 17 Oct 2012 19:05:04 +0000 http://andreynikolaev.wordpress.com/?p=1718#comment-480 Hello!
You should use ’full hash value‘ (KGLNAHSV) and NAMESPACE=>1
to mark PL/SQL function or procedure

Best Regards
Andrey Nikolaev

]]> Comment on Appetizer for DTrace by andreynikolaev http://andreynikolaev.wordpress.com/2010/10/28/appetizer-for-dtrace/#comment-479 Wed, 17 Oct 2012 18:25:24 +0000 http://andreynikolaev.wordpress.com/?p=417#comment-479 I think you are asking about AIX Probevue?
Yes, the simple scripts from this post can be rewritten for Probevue.

]]> Comment on Appetizer for DTrace by antony http://andreynikolaev.wordpress.com/2010/10/28/appetizer-for-dtrace/#comment-478 Wed, 17 Oct 2012 17:49:45 +0000 http://andreynikolaev.wordpress.com/?p=417#comment-478 Hi Andrey,

have you done similar test in AIX using procstack?

Thanks

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