Re: parsing puzzle

  • From: Cary Millsap <cary.millsap@xxxxxxxxxxxx>
  • To: andrew.kerber@xxxxxxxxx
  • Date: Fri, 9 Apr 2010 15:57:56 -0500

It's just really difficult to tell when AWR results are useful and when
they're not. That is what *unreliable* is, by definition. A problem with
even small snapshot intervals is that you're snapping data from potentially
thousands of sessions that can still bury the data you really need to be
looking at from one special session that you're trying to diagnose.

Cary Millsap
Method R Corporation

On Fri, Apr 9, 2010 at 2:51 PM, Andrew Kerber <andrew.kerber@xxxxxxxxx>wrote:

> That seems unlikely, the wait events are consistent.  However, If you want
> a short term snapshot though, run this command:
> exec dbms_workload_repository.create_snapshot
> at whatever interval you want.
> On Fri, Apr 9, 2010 at 2:22 PM, Allen, Brandon 
> <Brandon.Allen@xxxxxxxxxxx>wrote:
>> Because they report instance-wide stats, they could be showing you wait
>> events for processes that are completely unrelated to the problems you're
>> trying to troubleshoot.  And also since they are (usually) at infrequent
>> intervals, transient problems can easily be buried by other more persistent
>> events.  For example, a session that hangs for 5 minutes blocked by another
>> transaction's blocking lock - this 5 minute delay could be a major problem
>> for some business critical function that you're trying to troubleshoot, but
>> if you look at an AWR report over a 1 hour interval, those 5 minutes of
>> waiting on the blocking lock/enqueue aren't likely to show up in your top
>> wait events.
>> Regards,
>> Brandon
>> -----Original Message-----
>> From: Joe A-C [mailto:jwc7744@xxxxxxxxx]
>> Why do you say that the AWR reports are likely to be misleading?
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>> --
> --
> Andrew W. Kerber
> 'If at first you dont succeed, dont take up skydiving.'

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