Re: rebuild indexes

  • From: Maureen English <maureen.english@xxxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Fri, 18 Apr 2014 12:11:24 -0800

We use alter table ... shrink space cascade statement quite often for
a couple of tables from which we delete rows regularly.  You do need
to enable row movement before doing the shrink space, and then disable
row movement afterward.  For a table that's spread across 6G, I've seen
this process take many hours.  We don't rebuild the indexes after, but
I think that the cascade option also shrinks the indexes.

The advantages of shrink space over alter table ... move, include not
needing to have any additional space available for the table since it
is often quite large, and also not requiring any period of time when
the table isn't available to users.

- Maureen

On 4/18/2014 10:54 AM, Tim Gorman wrote:

ALTER TABLE ... MOVE (followed by index rebuilds) is one way to do this, but 
what they're probably asking for is ALTER
TABLE ... SHRINK, which can be done "online" and doesn't necessarily require 
index rebuild afterward.  More info here
<http://docs.oracle.com/cd/B28359_01/server.111/b28310/schema003.htm#ADMIN10161>.



On 4/18/2014 11:37 AM, Zelli, Brian wrote:


One table has 14 rows and the other has 26.  They say it is causing performance 
issues……

Brian

*From:*Andrew Kerber [mailto:andrew.kerber@xxxxxxxxx]
*Sent:* Friday, April 18, 2014 1:37 PM
*To:* Zelli, Brian
*Cc:* oracle-l (oracle-l@xxxxxxxxxxxxx)
*Subject:* Re: rebuild indexes

How big is the table?  He probably wants you to shrink it by eliminating unused 
blocks.  The simplest way to do that
is by an alter table move command followed by alter index rebuild.

Sent from my iPad


On Apr 18, 2014, at 12:26 PM, "Zelli, Brian" <Brian.Zelli@xxxxxxxxxxxxxxx 
<mailto:Brian.Zelli@xxxxxxxxxxxxxxx>> wrote:

    A vendor wants me to shrink a table. I’ve never shrunk one in oracle.  Does 
that delete the data out of them?

    And then wants me to rebuild the associated indexes.  Won’t they be empty 
after you shrink them?

    Brian


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Maureen English
Lead Database Administrator
University of Alaska
Fairbanks, AK
(907) 450-8329
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