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Re: What will be the rollback plan for a table move + index rebuild operation?

From: Powell, Mark <mark.powell2_at_dxc.com>
Date: Tue, 31 May 2022 18:20:48 +0000
Message-ID: <BY3PR01MB6674B0BF5879D600B60779B9CEDC9_at_BY3PR01MB6674.prod.exchangelabs.com> 








LOK, while it is technically possible that reorganizing a table/index can have an adverse performance impact I would not be that concerned.  Just check to see if any of the tables in your plan have non-default percent free reservations.  For example, if you have a table with a pctfree of 50 you probably want to lower the pctfree, perform the move, and set it back.  Otherwise you would create a lot of basically half full blocks that will never use the free space resulting in the need to read more blocks during a full table scan operation.  Likewise, an index range scan on the same values used before the table move could also have to visit more block after the rebuild.



An index rebuild can adversely impact an insert task if after the index rebuild significantly more block splits are required to support the inserts.  This issue tends to fix itself with additional running of the insert task.



Again, I would not be overly concerned, but you should always check the object space usage and parameter values in use before performing maintenance.  This should help you in spotting objects that may need special handling.





Mark Powell


Database Administration


(313) 592-5148






From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> on behalf of Pap <oracle.developer35_at_gmail.com>
Sent: Tuesday, May 31, 2022 12:19 PM


To: Lok P <loknath.73_at_gmail.com>


Cc: Oracle L <oracle-l_at_freelists.org>
Subject: Re: What will be the rollback plan for a table move + index rebuild operation?



You are rebuilding means just dropping and creating the same table and index without any change in structure and data pattern. So how can it affect the performance negatively?



On Tue, May 31, 2022 at 7:52 PM Lok P <loknath.73_at_gmail.com<mailto:loknath.73_at_gmail.com>> wrote:
As we are trying to move forward with table move+index rebuild operation to get some storage space back on a 12.1 version database. Management asks about the rollback plan just in case we see negative performance reading that table/index or while performing DML on the same table , post the table move+index rebuild operation. We don't have an exact lower environment with similar data volume and that too fragmented one to test application. So trying to understand, is there any way out here to get the exact fragmented table and index back in place as it was before?



Regards


Lok




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Received on Tue May 31 2022 - 20:20:48 CEST












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