Re: 9i / 9iRAC : Segment_Space_Management AUTO, with LOB

It would appear we're looking into yet another hit ratio, namely the ASS Hit Ratio. Used to be rather high in my younger days.

Mogens

Jonathan Lewis wrote:

>Depending on your circumstances, ASS Management
>can eliminate severe contention on the freelists / freelist
>groups area. However, because Oracle is overgenerous
>with its allocation of bitmap blocks (which may turn
>out to be in excess of 1% of your database), you
>may end up thrashing your system because most of
>your buffer space is flooded with hot BMBs and the
>data has to keep thrashing on and off disk.
>
>Regards
>
>Jonathan Lewis
>http://www.jlcomp.demon.co.uk
>
>Coming soon a new one-day tutorial:
>Cost Based Optimisation
>(see http://www.jlcomp.demon.co.uk/tutorial.html )
>
>Next Seminar dates:
>(see http://www.jlcomp.demon.co.uk/seminar.html )
>
>____England______January 21/23
>
>
>The Co-operative Oracle Users' FAQ
>http://www.jlcomp.demon.co.uk/faq/ind_faq.html
>
>
>
>
>
>-----Original Message-----
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>Date: 19 December 2002 17:51
>
>
>
>
>>We were the other way around in our testing lately:-)
>>
>>We turned on auto space management to remove the contention.
>>
>>
>Afterwards-we
>
>
>>removed quite a bit of header block/free list contention..
>>
>>anyway, more tests to follow
>>
>>-----Original Message-----
>>Sent: Thursday, December 19, 2002 10:09 AM
>>To: Multiple recipients of list ORACLE-L
>>
>>
>>
>>As part of a RAC benchmark with 9.2 we had faced severe LOCKING
>>on setting segment space management AUTO & had to REMOVE it
>>
>>HTH
>>
>>
>>
>
>
>
>

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