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	<title>Alberto Dell'Era's Oracle blog &#187; performance tuning</title>
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	<link>http://www.adellera.it/blog</link>
	<description>A blog about Oracle - Un blog riguardo Oracle</description>
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		<title>fast refresh of join-only MVs: _mv_refresh_use_stats and locking log stats</title>
		<link>http://www.adellera.it/blog/2010/03/11/fast-refresh-of-join-only-mvs-_mv_refresh_use_stats-and-locking-log-stats/</link>
		<comments>http://www.adellera.it/blog/2010/03/11/fast-refresh-of-join-only-mvs-_mv_refresh_use_stats-and-locking-log-stats/#comments</comments>
		<pubDate>Thu, 11 Mar 2010 20:46:16 +0000</pubDate>
		<dc:creator>Alberto Dell'Era</dc:creator>
				<category><![CDATA[materialized views]]></category>
		<category><![CDATA[performance tuning]]></category>

		<guid isPermaLink="false">http://www.adellera.it/blog/?p=426</guid>
		<description><![CDATA[A devastating performance degradation of materialized view fast refreshes can happen in versions after 9i - and can be healed rather easily by simply setting the hidden parameter _mv_refresh_use_stats or, a bit surprisingly, by locking statistics on the logs. The problem can manifest at least in the currently-latest patchsets of 10g, 11gR1 and 11gR2 (10.2.0.4, [...]]]></description>
		<wfw:commentRss>http://www.adellera.it/blog/2010/03/11/fast-refresh-of-join-only-mvs-_mv_refresh_use_stats-and-locking-log-stats/feed/</wfw:commentRss>
		<slash:comments>3</slash:comments>
		</item>
		<item>
		<title>xplan: dbms_metadata.get_ddl for tables referenced by the plan</title>
		<link>http://www.adellera.it/blog/2010/02/09/xplan-dbms_metadataget_ddl-for-tables-referenced-by-the-plan/</link>
		<comments>http://www.adellera.it/blog/2010/02/09/xplan-dbms_metadataget_ddl-for-tables-referenced-by-the-plan/#comments</comments>
		<pubDate>Tue, 09 Feb 2010 15:59:40 +0000</pubDate>
		<dc:creator>Alberto Dell'Era</dc:creator>
				<category><![CDATA[performance tuning]]></category>
		<category><![CDATA[tools]]></category>
		<category><![CDATA[xplan]]></category>

		<guid isPermaLink="false">http://www.adellera.it/blog/?p=417</guid>
		<description><![CDATA[As a minor but useful new feature, xplan is now able to integrate into its report the DDL of tables (and indexes) referenced by the plan, calling dbms_metadata.get_ddl transparently. 
This is mostly useful to get more details about referenced tables' constraints and partitions definition - to complement their CBO-related statistics that xplan reports about.
This feature [...]]]></description>
		<wfw:commentRss>http://www.adellera.it/blog/2010/02/09/xplan-dbms_metadataget_ddl-for-tables-referenced-by-the-plan/feed/</wfw:commentRss>
		<slash:comments>1</slash:comments>
		</item>
		<item>
		<title>11gR2: new algorithm for fast refresh of on-commit materialized views</title>
		<link>http://www.adellera.it/blog/2009/11/22/11gr2-new-algorithm-for-fast-refresh-of-on-commit-materialized-views/</link>
		<comments>http://www.adellera.it/blog/2009/11/22/11gr2-new-algorithm-for-fast-refresh-of-on-commit-materialized-views/#comments</comments>
		<pubDate>Sun, 22 Nov 2009 15:56:28 +0000</pubDate>
		<dc:creator>Alberto Dell'Era</dc:creator>
				<category><![CDATA[materialized views]]></category>
		<category><![CDATA[performance tuning]]></category>

		<guid isPermaLink="false">http://www.adellera.it/blog/?p=385</guid>
		<description><![CDATA[This post investigates the improvements that have been made in 11gR2 to the fast refresh engine of materialized views (MVs) that are set to be automatically refreshed at commit time. We speak about join-only materialized views only in this post, as always with the help of a test case.
As noted in the post of mine [...]]]></description>
		<wfw:commentRss>http://www.adellera.it/blog/2009/11/22/11gr2-new-algorithm-for-fast-refresh-of-on-commit-materialized-views/feed/</wfw:commentRss>
		<slash:comments>8</slash:comments>
		</item>
		<item>
		<title>CBO: the &#8220;non-empty result set&#8221; assumption</title>
		<link>http://www.adellera.it/blog/2009/09/03/cbo-the-non-empty-result-set-assumption/</link>
		<comments>http://www.adellera.it/blog/2009/09/03/cbo-the-non-empty-result-set-assumption/#comments</comments>
		<pubDate>Thu, 03 Sep 2009 13:14:58 +0000</pubDate>
		<dc:creator>Alberto Dell'Era</dc:creator>
				<category><![CDATA[CBO]]></category>
		<category><![CDATA[performance tuning]]></category>

		<guid isPermaLink="false">http://www.adellera.it/blog/?p=322</guid>
		<description><![CDATA[The CBO assumes that SELECT statements are always going to retrieve at least one row - even if this is not necessarily the case, of course. Understanding why this is done is both useful and fascinating.
We must start from the very beginning and remember that one of the most important tasks of the CBO is [...]]]></description>
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		<slash:comments>6</slash:comments>
		</item>
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		<title>Xplan 2.0</title>
		<link>http://www.adellera.it/blog/2009/08/07/xplan-20/</link>
		<comments>http://www.adellera.it/blog/2009/08/07/xplan-20/#comments</comments>
		<pubDate>Fri, 07 Aug 2009 08:11:08 +0000</pubDate>
		<dc:creator>Alberto Dell'Era</dc:creator>
				<category><![CDATA[performance tuning]]></category>
		<category><![CDATA[tools]]></category>
		<category><![CDATA[xplan]]></category>

		<guid isPermaLink="false">http://www.adellera.it/blog/?p=285</guid>
		<description><![CDATA[A lot of new features have been added in version 2.0 of xplan, the sqlplus script I use to investigate about SQL statements performance (I spoke about version 1.0 in this post). Here's a brief description.
wait profile (from ASH)
For each statement, its wait profile is calculated fetching wait information from Active Session History:

-----------------------------------------
&#124;ash event  [...]]]></description>
		<wfw:commentRss>http://www.adellera.it/blog/2009/08/07/xplan-20/feed/</wfw:commentRss>
		<slash:comments>15</slash:comments>
		</item>
		<item>
		<title>Tuning Oracle for Siebel &#8211; SQL template</title>
		<link>http://www.adellera.it/blog/2009/06/30/tuning-oracle-for-siebel-sql-template/</link>
		<comments>http://www.adellera.it/blog/2009/06/30/tuning-oracle-for-siebel-sql-template/#comments</comments>
		<pubDate>Mon, 29 Jun 2009 22:31:04 +0000</pubDate>
		<dc:creator>Alberto Dell'Era</dc:creator>
				<category><![CDATA[performance tuning]]></category>
		<category><![CDATA[siebel]]></category>

		<guid isPermaLink="false">http://www.adellera.it/blog/?p=267</guid>
		<description><![CDATA[The time has come to write down some of the most relevant discoveries I've made so far while being part of a team that is tuning a huge Siebel installation for a leading Italian company ("huge" especially because of the user base dimension and secondarily because of the hardware deployed, a three-node RAC on pretty [...]]]></description>
		<wfw:commentRss>http://www.adellera.it/blog/2009/06/30/tuning-oracle-for-siebel-sql-template/feed/</wfw:commentRss>
		<slash:comments>8</slash:comments>
		</item>
		<item>
		<title>Optimizing SQL statements with xplan</title>
		<link>http://www.adellera.it/blog/2009/06/07/optimizing-sql-statements-with-xplan/</link>
		<comments>http://www.adellera.it/blog/2009/06/07/optimizing-sql-statements-with-xplan/#comments</comments>
		<pubDate>Sun, 07 Jun 2009 15:07:06 +0000</pubDate>
		<dc:creator>Alberto Dell'Era</dc:creator>
				<category><![CDATA[performance tuning]]></category>
		<category><![CDATA[tools]]></category>

		<guid isPermaLink="false">http://www.adellera.it/blog/?p=259</guid>
		<description><![CDATA[Xplan is a utility to simplify and automate the first part of every SQL statement tuning effort, that is, collecting the real plan of the statement, its execution statistics (number of executions, number of buffer gets performed, etc), getting the definition of all the accessed tables (and their indexes), and, last but not least, the [...]]]></description>
		<wfw:commentRss>http://www.adellera.it/blog/2009/06/07/optimizing-sql-statements-with-xplan/feed/</wfw:commentRss>
		<slash:comments>10</slash:comments>
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