Re: table shrink

From: Adam Musch <>
Date: Mon, 7 Dec 2009 09:58:01 -0600
Message-ID: <>

Remember, if it's moving rows (and therefore, changing ROWIDs), it's also got indexes to update. So it could require significantly more UNDO than the size of the table. If you can afford the downtime, you may be better off with impdp/expdp, alter table move, and/or online table redefinition.

On Mon, Dec 7, 2009 at 9:46 AM, <> wrote:
> Hello everyone:
> I am researching alter table shrink space command in before I try
> it in production. According to oracle adviser, there is a table that can be
> shrank
> to release over 40G of space and another which can release over 100G. I
> plan to execute the commands during a maintenance window to minimize the
> usage of these tables.  I have run a small test in dev and saw that these
> command have been using undo tablespace. That tablespace is only 20G
> in my database. Does it need to match the size of the 'freeable' disk
> space, in other word do I need to increase it to about 100G? I also was
> told that
> i can cancel this command any time (in case there is a performance
> degradation) and whatever disk space has been released will stay released
> and
> I can run the command again to release the rest of the disk space. I have
> not been able to find this in any oracle documentation however. I don't
> have any table in dev to test a large shrink command.
> If anyone had any experience with this command, can you please address my
> questions on undo TS and cancelling the command please. I am
> alsowondering whether there is any downside to this operation.
> Thank you
> Eugene Gurevich
> Please consider the environment before printing this email.
> --

Adam Musch
Received on Mon Dec 07 2009 - 09:58:01 CST

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