Re: Enterprise slow, Standard fast?

DA Morgan wrote:
> Arska wrote:
>
>> Mladen Gogala wrote:
>>
>>> On Sun, 07 Nov 2004 20:38:32 +0200, Arska wrote:
>>>
>>>
>>>> Now we need to tune every job again, parallel execution in mind.
>>>> Or deny parallel execution for these jobs. (How?)
>>>
>>>
>>>
>>> No! You should just tune the buffer cache hit ratio. When it is
>>> close to 100%, your performance is good. Make sure that BCHR
>>> reports are compiled and run every morning. The job of a DBA is
>>> to maintain the highest cache hit ratio possible. DBAs are the
>>> priests of the buffer cache god. You shouldn't be tuning
>>> applications, but the instance. Users are not running
>>> applications, they're running instance, so that's what you tune.
>>> That means that all you have to do is to fiddle and twist the
>>> buffer cache parameters and everything will be good. Make sure
>>> that 99% of cache hit ratio is entered into the official company
>>> documentation as the ultimate performance metrics.
>>
>> Buffer cache is currently 1008 MB, and cache hit ratio is 98.9%
>> after running few heavy update jobs. Are you saying I need to buy
>> more RAM and increase buffer cache? I dont think so.
>> We only need to add "ALTER SESSION DISABLE PARALLEL QUERY" to all
>> jobs, which was slow with EE, and magically they are fast again.
>>
>> Parallel query does add some overhead. Usually it is still faster,
>> but not always. In this case it is better not to use it.
>
> If he is I wouldn't take his advice.
>
> You might want to get a copy of:
> Why a 99%+ Database Buffer Cache Hit Ratio is Not Ok by Cary Millsap

Additionally you might want to download his code examples at http://examples.oreilly.com/optoraclep/
(more specific, the 'set-bcr.pl' script)

These examples are extracted from his book 'Optimizing Oracle Performance' (O'Reilly).

-- 
Jeroen