Re: online index rebuilds

From: Tanel Põder <tanel.poder.003_at_mail.ee>
Date: Mon, 30 Jan 2006 13:58:20 -0600
Message-ID: <055c01c625d7$8a877f90$c6bc21c8@porgand>

Hi,

Thinking about why full table scan is required for online index rebuild... Maybe the potential index block splits are the reason why index FFS can't be used for online index rebuild? Consistent reads should overcome this issue though, but maybe there is something we don't know...

Btw, with offline index rebuild the decision whether to go with FTS or index FFS is also cost based (at least 10.2). If I have only single-column table indexed then the offline rebuild may do an FTS instead of fasf full index scan. (also, even in the case of fast full index scan, rows have to be sorted anyway, because index fast full scan doesn't guarantee an ordered result).

Tanel.

Original Message ----- From: Roger Xu To: joseph_at_amalrajinc.com ; Bobak, Mark ; ORACLE-L Cc: tanel.poder.003_at_mail.ee Sent: Wednesday, January 25, 2006 2:05 PM Subject: online index rebuilds

Any other differences besides: 1) does not lock the table; 2) does a full table scan instead of full index scan; ? -----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Joseph Amalraj Sent: Tuesday, January 24, 2006 9:48 AM To: Bobak, Mark; joseph_at_amalrajinc.com; ORACLE-L Subject: RE: ORA-01652: unable to extend temp segment

Thanks,

Had read the article, but I am interested as to why Oracle is doing a full table scan instead of full index scan for online index rebuilds.

"Bobak, Mark" <Mark.Bobak_at_il.proquest.com> wrote: Well, my name is not Tanel, but I'll jump in here and point you to MetaLink Doc ID 272762.1.

      -Mark
      -- 
      Mark J. Bobak 
      Senior Oracle Architect 
      ProQuest Information & Learning 
      "There are 10 types of people in the world:  Those who understand binary, and those who don't." 




--------------------------------------------------------------------------
      From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Joseph Amalraj
      Sent: Tuesday, January 24, 2006 9:59 AM
      To: ORACLE-L
      Subject: Re: ORA-01652: unable to extend temp segment


      Thanks Tanel, 

      Is there any reason why Oracle does full table scans for online rebuilds and not for offline.

      Regards

      Joseph Amalraj

      Tanel Põder <tanel.poder.003_at_mail.ee> wrote:
        Online rebuilds don't use existing index for creating new. They do full table scan on the table.

        However, in both cases, old index segment is kept until new one is ready to use and switch to it is done. Also the journal IOTs used for online rebuilds are stored in the target tablespace, so if you've got lots of transaction s going on while you are rebuilding the index onl ine, you need additional space in target tablespace.

        Tanel.

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Received on Mon Jan 30 2006 - 13:58:20 CST