Re: Oracle slowed down

From: ianal Vista <ianal_vista_at_hotmail.com>
Date: Sun, 23 Apr 2006 01:21:43 GMT
Message-ID: <Xns97ADBAD5D37E5ianalvistahotmailcom@70.169.32.36>

"Bob Jones" <email_at_me.not> wrote in
news:5oz2g.13722$4L1.13455_at_newssvr11.news.prodigy.com:

>
> "ianal Vista" <ianal_vista_at_hotmail.com> wrote in message
> news:Xns97ADAA1CDFD1Dianalvistahotmailcom_at_70.169.32.36...

>> "Bob Jones" <email_at_me.not> wrote in news:IXy2g.13714$4L1.12286
>> @newssvr11.news.prodigy.com:
>>
>>>
>>> "HansF" <News.Hans_at_telus.net> wrote in message
>>> news:pan.2006.04.22.22.14.55.540761_at_telus.net...
>>>> On Sat, 22 Apr 2006 22:56:20 +0000, Bob Jones wrote:
>>>>
>>>>> The only thing I disagree with here is that BCHR is deprecated or
>>>>> irrelevant.
>>>>
>>>> Not deprecated does not imply relevant.
>>>>
>>>
>>> No, it does not. BCHR is neither deprecated nor irrelevant.
>>>
>>>
>>
>> Since the BCHR can be achieved at what ever value that is desired,
>> how is BCHR relevant & to who?

>
> To people who make distinction between application tuning and buffer
> cache tuning.
>
>
>

http://asktom.oracle.com/pls/ask/f?p=
4950:8:11500305522999310977::NO::F4950_P8_DISPLAYID,F4950_P8 _CRITERIA:4973488577582 http://www.hotsos.com/e-library/abstract.php?id=6

"Abstract: Many tuning professionals and textbook authors sell advice encouraging their customers to enjoy the performance virtues of Oracle database buffer cache hit ratios that approach 100%. However, database buffer cache hit ratio is not a reliable system performance metric. Buffer cache hit ratios above 99% usually indicate particularly serious SQL inefficiencies. Repairs of these inefficiencies often yield 100x or greater performance improvements, yet the optimizations result in reduced database buffer cache hit ratios. This paper shows why a 99%+ buffer cache hit ratio almost always signals performance inefficiencies, including real-life examples. It shows how to detect the inefficiencies and how to repair them. It concludes with recommendations about what metrics the performance analyst should use instead of the venerable but

unreliable database buffer cache hit ratio."
^^^^^^^^^^

Received on Sat Apr 22 2006 - 20:21:43 CDT