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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Move table online and update the indexes at the same time.
Thanks Tanel. Excellent presentation.
Revision:
Freelist information that has to be changed to add freelists does not reside in individual blocks.
While you're on the freelist, you've got a pointer to the next block in the
free list (and are being
pointed to by the previous block.)
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Tanel Põder
Sent: Wednesday, July 28, 2004 11:21 AM
To: oracle-l_at_freelists.org
Subject: Re: Move table online and update the indexes at the same time.
Hi!
> You should only need to use rebuild freelists if your freelists are in
some
> way "broken."
Or block space is inefficiently used due prematurely unlinked blocks (caused by highly varying row sizes and suboptimal pctfree/used parameters).
<<<< agreed, I just consider that "broken," and if he is insert oriented, he'll burn those up in time.
>
> Freelist information does not reside in individual blocks.
Actually every datablock has a pointer to next block in freelist. Segment header (or freelist group block) just has pointer to first block that would be considered for insert (thus being in freelist), this block contains pointer to next one etc...
> segment allocation is from the tablespace (relatively big overhead)
> master freelist keeps some free headroom in reserve and gets back blocks
> that get "empty enough." If the master freelist runs low on demand, bump
> goes the high water mark, and if needed gets some segment allocation.
Its somewhat more complicated - "free" blocks go to master freelist in rare cases, like fixing freelist information, some cases with HWM increasing, usually the free blocks will stay in process freelists or transaction freelists.
<<<< Ouch. I thought between 6.2 and 7.1 that changed to keep imbalance between groups small, but I never went back and <<<< checked it. I guess minimizing changes was more important. Anyway, your presentation is wonderful, even without the <<<< talk to go with it.
You could get some additional information out from http://integrid.info/Poder_Freelists_vs_ASSM.ppt
Tanel.
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