RE: Library Cache and Share wait on Latch - Version Count Huge

  • From: "Mudhalvan Moovarkku" <moovarkku.mudhalvan@xxxxxxxxxxxxxxxx>
  • To: "Tanel Poder" <tanel@xxxxxxxxxx>
  • Date: Thu, 18 Mar 2010 12:22:46 +0900


   Thanks a lot and found I can not delete all histogram as you have


  Now I know only few SQL have the multiple PLAN_HASH_VALUE. I think I
have remove only related columns histogram. Could you please confirm and
the method if you already done before.


select hash_value,plan_hash_value,count(*) from v$sql where sql_text
like '%:"SYS_B_0"%' group by hash_value,plan_hash_value;



3722612061       3351193255       113

1983846182       3351193255       112

2831213151       2975737795       21



Mudhalvan M.M 


From: Tanel Poder [mailto:tanel@xxxxxxxxxx] 
Sent: Thursday, March 18, 2010 9:44 AM
To: Mudhalvan Moovarkku
Cc: Oracle-L@xxxxxxxxxxxxx
Subject: Re: Library Cache and Share wait on Latch - Version Count Huge


After setting method_opt to REPEAT you will also need to manually drop
all the histograms, as they have been already created for you.


However I don't know your application/data, maybe you do need some
histograms somewhere, so you need to review the histograms you have
yourself and decide whether it's ok to get rid of them. If it's purely
an OLTP system with bind variables used everywhere, its probably ok to
get rid of all histograms as histograms and bind variables are a deadly
combination anyway - for stable performance.

Tanel Poder

On Thu, Mar 18, 2010 at 8:38 AM, Mudhalvan Moovarkku
<moovarkku.mudhalvan@xxxxxxxxxxxxxxxx> wrote:

Hi Tanel

            Thanks for your suggestion. 


            I am very sorry due the bad application we will not be able
to change SIMILAR to FORCE. 


            So I have to clear the Histograms


            I this METHOD_OPT from AUTO to REPEAT will help me. 


I will check on the dbms_stats.get_param and change it to REPEAT if no


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