RE: GTT and Undo and Redo
- From: Jonathan Lewis <jonathan@xxxxxxxxxxxxxxxxxx>
- To: "Hemant-K.Chitale@xxxxxx" <Hemant-K.Chitale@xxxxxx>, ORACLE-L <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 28 Feb 2014 09:44:58 +0000
Should have pointed out that the answers applied to your 11.2 question.
Things change in 12c where you can enable "temp undo" - which means the undo
for operations on GTTs goes to the database default temporary tablespace.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
@jloracle
________________________________
From: Jonathan Lewis
Sent: 28 February 2014 09:42
To: Hemant-K.Chitale@xxxxxx; ORACLE-L
Subject: RE: GTT and Undo and Redo
Note inline
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
@jloracle
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx [oracle-l-bounce@xxxxxxxxxxxxx] on behalf
of Chitale, Hemant K [Hemant-K.Chitale@xxxxxx]
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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