Re: Shared pool wait for library cache pin

George/Arun,

Thanks for your helpful replies. This information may help me explain the performance problems that peaked yesterday.

I do have timed_statistics set to true and my version is 8.1.5.

How do you define whether a version count is "high" ? Is there some threshould that you cross when it becomes "high". Is it a percentage of total statements or users or what?

This problem seems to have creeped up on us over time. After I flushed the shared pool yesterday, we seem to be o.k. right now. Our application owner is concerned that this problem may recur.

If we do indeed have this bug, then our only recourse seems to be either to upgrade to 8.1.7.x or to use the work-around of flushing the shared pool, right?

Thanks for taking time to reply.

Cherie

                                                                                       
                         
                    George                                                             
                         
                    Schlossnagle           To:     Multiple recipients of list 
ORACLE-L <ORACLE-L_at_fatcity.com>  
                    <schlossnagle_at_py       cc:                                         
                         
                    thian.com>             Subject:     Re: Shared pool wait for 
library cache pin              
                    Sent by:                                                           
                         
                    root_at_fatcity.com                                                   
                         
                                                                                       
                         
                                                                                       
                         
                    01/03/02 12:50                                                     
                         
                    AM                                                                 
                         
                    Please respond                                                     
                         
                    to ORACLE-L                                                        
                         
                                                                                       
                         
                                                                                       
                         

Hi,

Queries with high version counts can cause library cache latch contention, as the query must hold that latch during soft parse and has to go through the entire list of query versions in the data dictionary. High version_count's are often caused by a high number of invalidations on the query. Invalidations of a query can be caused by a number of different things (one is the bug with timed_statistics, another is a bug present up to 8.1.6.3 in some instances when materialized views are used), other causes of invalidations are analyzing a dependent table or index, or truncating a dependent table.

If this is causing you a problem, the next step is to track down what the cause of your high version_counts is, and work to correct it or workaround it (depending on the frequency that the query is executed, a shared pool flush may remove all versions (or none)). If it's not causing you a service problem currently, I would still keep an eye on it, as the version_count for queries rises, the chances of getting severe contention on the library cache latch increases.

George

// George Schlossnagle
// www.pythian.com -- schlossnagle_at_pythian.com -- 877-PYTHIAN
// Smarter than adding another team member, Pythian has new services
// for supplementing DBAs: get our help with monitoring, 24x7 on-call,
// daily verifications, storage management, performance and more.

On Wednesday, January 2, 2002, at 04:35 PM, Cherie_Machler_at_gelco.com wrote:

>
> Yes, there are a handful with more than 400.
> I'm not sure what high is?
>
> Cherie
>
>
>
> "George
> Schlossnagle" To: Multiple recipients
> of list ORACLE-L <ORACLE-L_at_fatcity.com>
> <schlossnagle_at_py cc:
> thian.com> Subject: Re: Shared pool
> wait for library cache pin
> Sent by:
> root_at_fatcity.com
>
>
> 01/02/02 02:41
> PM
> Please respond
> to ORACLE-L
>
>
>
>
>
>
> Do any of your queries have a high version_count (visible through
> v$sqlarea)?
>
> George
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Wednesday, January 02, 2002 3:20 PM
>
>
>>
>> We are seeing a lot of shared pool waits (for libary cache pin) on
>> our 8.1.5 web-based application. We are seeing this via
>> Precise/Indepth
>> SQL monitoring tool.
>>
>> I haven't been able to find much documentation on shared pool waits or
>> library cache pins.
>>
>> Can anyone tell me what might be causing this problem?
>>
>> Thanks,
>>
>> Cherie
>>
>> --
>> Please see the official ORACLE-L FAQ: http://www.orafaq.com
>> --
>> Author:
>> INET: Cherie_Machler_at_gelco.com
>>
>> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
>> San Diego, California -- Public Internet access / Mailing Lists
>> --------------------------------------------------------------------
>> To REMOVE yourself from this mailing list, send an E-Mail message
>> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
>> the message BODY, include a line containing: UNSUB ORACLE-L
>> (or the name of mailing list you want to be removed from). You may
>> also send the HELP command for other information (like subscribing).
>>
>>
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: George Schlossnagle
> INET: schlossnagle_at_pythian.com
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
> --------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
>
>
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author:
> INET: Cherie_Machler_at_gelco.com
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
> --------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
>
>

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: 
  INET: Cherie_Machler_at_gelco.com

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).