RE: missed Anjo's webcast..

First, I didn't see the broadcast. I believe the claim that a high BHR may not indicate a healthy system, has become it is always indicative of an unhealthy system. Egad, by BHR is over 90% and no users are are complaining, I better start tinkering! Isn't the idea that BHR is an unreliable indicator .  

Here are two statements :          

                 select a.chnum, sum(a.f) f from rollup a where a.effdt=(select max(b.effdt)
                 from rollup b where a.chnum=b.chnum)  
                 group by a.chnum
 
 
   
  

-----Original Message-----
Sent: Thursday, August 08, 2002 1:31 PM
To: Multiple recipients of list ORACLE-L

Well, I guess that I disagree. Buffer hit radio does matter as one of the performance indicators, but certainly not the only one. Your and Mr. Milsap thesis is that LIO also is very expensive and its cost is far from being negligible, so having gazillion of LIOs instead of 100 times smaller number of PIOs will not make our system run faster. BHR alone cannot be used to judge to overall health of the system, but thebn again, there is no such thing as the "overall health of the system". It's the users of the system who will say whether the performance is satisfactory or not, and I'm usually tuning an application, not an imaginary "overall system". Low cache hit ratio usually tells me that I do have a hog who is using lots of PIOs. By my experience, it usually is a very good indicator that something is wrong, at least on an OLTP  system. So, after all, I do find BHR a useful indicator, but by no means the only one or the most important one. Event 10046, SQL_TRACE (level 1 of 10046), explain plan and v$session_event still are the tools I need most, but I still do need BHR as an indicator.

Mladen Gogala
Oracle DBA
Phone: (203) 459-6855
Email: mgogala_at_oxhp.com

-----Original Message-----
Sent: Thursday, August 08, 2002 1:05 PM
To: Multiple recipients of list ORACLE-L

Moi wrong ;-) Jeeh, human after all  

To summarize the webcast:
db-block-buffers do mattter. Too many LIO do matter. Too many PIO do matter. But Buffer Cache Hit ratio doesn't matter ....... End user satisfaction does matter.  

I am always willing to clarify any points that I made, you just have to ask me l ....  

Anjo.    

• Original Message -----

To: Multiple recipients of list <mailto:ORACLE-L_at_fatcity.com> ORACLE-L Sent: Thursday, August 08, 2002 5:43 PM

Guys,

I had this dream that I missed the webcast - which I did. However, someone said it wasn't very interesting but the conversation of the people (gurus) left over was very interesting as there was good solid evidence that he was incorrect and db_block_buffers do matter. Kind of inline with the discussion about redos yesterday and my indexing/partition issues - hmmm.

-----Original Message-----
Sent: Thursday, August 08, 2002 1:38 AM To: Multiple recipients of list ORACLE-L

Www.precise.com, go to Events->webcasts... On 2002.08.08 00:53 Madhusudhanan Sampath wrote:
> Are transcript documents available anywhere?
>
> Regards
> Madhusudhanan S
>
>
>
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