RE: GTT and Undo and Redo
Date: Fri, 28 Feb 2014 09:42:52 +0000
Message-ID: <CE70217733273F49A8A162EE074F64D901DE0856_at_exmbx05.thus.corp>
Note inline
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
_at_jloracle
From: oracle-l-bounce_at_freelists.org [oracle-l-bounce_at_freelists.org] on behalf of Chitale, Hemant K [Hemant-K.Chitale_at_sc.com] Sent: 28 February 2014 09:14
To: ORACLE-L
Subject: GTT and Undo and Redo
GTT in 11.2
Quick question or clarification :
No Redo is generated for an Insert into a GTT
>> Correct, if you ignore the redo generated to describe the undo
There is Undo generated
>> Correct
Questions :
If we do a Direct Path Insert / Parallel Insert into the GTT can we avoid/reduce the Undo as well (and the Redo for the Undo) ?
>> Yes, but you'll have to commit, so the GTT will have to be "on commit preserve rows"
If there is an Index on the GTT, undo is generated for the index as well – what about a Direct Path Insert ?
>> Still generated, but for direct path insert (generically) Oracle optimizes the generation of redo and undo,
>> so the undo (and redo for undo) for the index could be reduced.
>> The scale of the difference will depend on whether or not the GTT already holds data, and how much
How does this work in a FORCE_LOGGING database ? Does it force redo for all direct path operations against a GTT and Index on GTT ? My Test environment doesn’t have FORCE_LOGGING (and I am not the DBA) so I can’t test this.
>> The temporary tablespace is not logged even when database force_logging is enabled
Hemant K Chitale
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