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	<title>Striving for Optimal Performance &#187; Bug</title>
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	<link>http://antognini.ch</link>
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		<title>Exadata Storage Server and the Query Optimizer – Part 4</title>
		<link>http://antognini.ch/2010/08/exadata-storage-server-and-the-query-optimizer-%e2%80%93-part-4/</link>
		<comments>http://antognini.ch/2010/08/exadata-storage-server-and-the-query-optimizer-%e2%80%93-part-4/#comments</comments>
		<pubDate>Mon, 09 Aug 2010 15:37:40 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[11gR2]]></category>
		<category><![CDATA[Bug]]></category>
		<category><![CDATA[Exadata]]></category>
		<category><![CDATA[Query Optimizer]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=1227</guid>
		<description><![CDATA[When I started writing the series of posts about Exadata Storage Server and the query optimizer, I didn’t expect to write more than three posts (part 1, part 2, part 3). Of course, things change. Hence, here is part 4 to cover a couple of things that I learned in the next couple of months.
In [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2010/08/exadata-storage-server-and-the-query-optimizer-%e2%80%93-part-4/feed/</wfw:commentRss>
		<slash:comments>1</slash:comments>
		</item>
		<item>
		<title>Optimizer Mode Mismatch Does Not Prevent Sharing of Child Cursor!?!?</title>
		<link>http://antognini.ch/2010/06/optimizer-mode-mismatch-does-not-prevent-sharing-of-child-cursor/</link>
		<comments>http://antognini.ch/2010/06/optimizer-mode-mismatch-does-not-prevent-sharing-of-child-cursor/#comments</comments>
		<pubDate>Thu, 03 Jun 2010 17:40:03 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[10gR1]]></category>
		<category><![CDATA[10gR2]]></category>
		<category><![CDATA[11gR1]]></category>
		<category><![CDATA[11gR2]]></category>
		<category><![CDATA[9iR2]]></category>
		<category><![CDATA[Bug]]></category>
		<category><![CDATA[Query Optimizer]]></category>
		<category><![CDATA[SQL Trace]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=1113</guid>
		<description><![CDATA[The aim of this post is to describe a strange (buggy) situation that I observed recently. But before doing that, I shortly summarize what a parent cursor and a child cursor are as well as when they can be shared. By the way, I borrowed this description from the pages 20/21 of my book. Hence, [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2010/06/optimizer-mode-mismatch-does-not-prevent-sharing-of-child-cursor/feed/</wfw:commentRss>
		<slash:comments>2</slash:comments>
		</item>
		<item>
		<title>How Good Are the Values Returned by DBMS_COMPRESSION.GET_COMPRESSION_RATIO?</title>
		<link>http://antognini.ch/2010/05/how-good-are-the-values-returned-by-dbms_compression-get_compression_ratio/</link>
		<comments>http://antognini.ch/2010/05/how-good-are-the-values-returned-by-dbms_compression-get_compression_ratio/#comments</comments>
		<pubDate>Thu, 20 May 2010 00:00:17 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[11gR2]]></category>
		<category><![CDATA[Bug]]></category>
		<category><![CDATA[Exadata]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=1078</guid>
		<description><![CDATA[According to the documentation the GET_COMPRESSION_RATIO procedure of the DBMS_COMPRESSION package can be used to assess the impact of different compression options for a given table. In other words, it allows us to find out the expected compression ratio for a given set of data without having to really create a compressed table. The question [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2010/05/how-good-are-the-values-returned-by-dbms_compression-get_compression_ratio/feed/</wfw:commentRss>
		<slash:comments>10</slash:comments>
		</item>
		<item>
		<title>A-Rows and DML Statements</title>
		<link>http://antognini.ch/2009/07/a-rows-and-dml-statements/</link>
		<comments>http://antognini.ch/2009/07/a-rows-and-dml-statements/#comments</comments>
		<pubDate>Fri, 31 Jul 2009 10:15:30 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[10gR1]]></category>
		<category><![CDATA[10gR2]]></category>
		<category><![CDATA[11gR1]]></category>
		<category><![CDATA[9iR2]]></category>
		<category><![CDATA[Bug]]></category>
		<category><![CDATA[TOP]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=444</guid>
		<description><![CDATA[Today&#8217;s post is dedicated to the Metalink SR identified by the number 6468252.994. I know, this number says nothing to you. For me, however, it’s a very well known number. The reason is quite simple… Even if I open this SR almost two years ago (to be precise, September 5, 2007), it was closed few [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2009/07/a-rows-and-dml-statements/feed/</wfw:commentRss>
		<slash:comments>4</slash:comments>
		</item>
		<item>
		<title>Wrong Information about Temporary Space Usage in V$SQL_PLAN_STATISTICS_ALL and DBMS_XPLAN Output</title>
		<link>http://antognini.ch/2009/05/wrong-information-about-temporary-space-usage/</link>
		<comments>http://antognini.ch/2009/05/wrong-information-about-temporary-space-usage/#comments</comments>
		<pubDate>Tue, 05 May 2009 00:00:20 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[10gR1]]></category>
		<category><![CDATA[10gR2]]></category>
		<category><![CDATA[11gR1]]></category>
		<category><![CDATA[Bug]]></category>
		<category><![CDATA[TOP]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=271</guid>
		<description><![CDATA[As you can read in the documentation, the columns MAX_TEMPSEG_SIZE and LAST_TEMPSEG_SIZE in the dynamic performance view V$SQL_WORKAREA provide information about the size of the temporary segment used for a specific workarea. The values are given in bytes. Let&#8217;s perform a test to check this information&#8230;

Create a test table that contains about 1MB of data:

SQL&#62; [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2009/05/wrong-information-about-temporary-space-usage/feed/</wfw:commentRss>
		<slash:comments>8</slash:comments>
		</item>
		<item>
		<title>Virtual Column-Based Partitioning Might Lead to Wrong Results</title>
		<link>http://antognini.ch/2009/02/virtual-column-based-partitioning-might-lead-to-wrong-results/</link>
		<comments>http://antognini.ch/2009/02/virtual-column-based-partitioning-might-lead-to-wrong-results/#comments</comments>
		<pubDate>Tue, 17 Feb 2009 06:53:31 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[11gR1]]></category>
		<category><![CDATA[Bug]]></category>
		<category><![CDATA[Partitioning]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=77</guid>
		<description><![CDATA[As of Oracle Database 11g it is possible to use a virtual column as partition key. In this post I do not want to discuss how it works and whether this is good or not&#8230; Instead, I would like to show you that the feature might lead to wrong results. 
First of all, I would [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2009/02/virtual-column-based-partitioning-might-lead-to-wrong-results/feed/</wfw:commentRss>
		<slash:comments>3</slash:comments>
		</item>
		<item>
		<title>Oracle AD4J Installation on Linux</title>
		<link>http://antognini.ch/2009/02/oracle-ad4j-installation-on-linux/</link>
		<comments>http://antognini.ch/2009/02/oracle-ad4j-installation-on-linux/#comments</comments>
		<pubDate>Fri, 13 Feb 2009 10:37:49 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[Bug]]></category>
		<category><![CDATA[Oracle AD4J]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=70</guid>
		<description><![CDATA[Today I tried to install Oracle AD4J on a Linux server that I have at home. The installation procedure is really simple and fully described here. Unfortunately, when I tried to access the console for the first time (that access is one of the installation steps), the HTTP server returned an internal server error (500). [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2009/02/oracle-ad4j-installation-on-linux/feed/</wfw:commentRss>
		<slash:comments>6</slash:comments>
		</item>
		<item>
		<title>Invisible Indexes and Hints</title>
		<link>http://antognini.ch/2008/11/invisible-indexes-and-hints/</link>
		<comments>http://antognini.ch/2008/11/invisible-indexes-and-hints/#comments</comments>
		<pubDate>Tue, 11 Nov 2008 16:02:32 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[11gR1]]></category>
		<category><![CDATA[Bug]]></category>
		<category><![CDATA[Indexes]]></category>
		<category><![CDATA[Query Optimizer]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=56</guid>
		<description><![CDATA[In this post I would like to remove some misinformation about the utilization of hints with invisible indexes.
Let’s start by providing you what two sources say about that topic:

Oracle Database 11g: New Features for DBAs and Developers (by Sam R. Alapati and Charles Kim, page 132)
“If you want the optimizer to take the invisible index [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2008/11/invisible-indexes-and-hints/feed/</wfw:commentRss>
		<slash:comments>5</slash:comments>
		</item>
		<item>
		<title>Long Parses</title>
		<link>http://antognini.ch/2008/08/long-parses/</link>
		<comments>http://antognini.ch/2008/08/long-parses/#comments</comments>
		<pubDate>Sun, 31 Aug 2008 10:21:14 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[10gR2]]></category>
		<category><![CDATA[9iR2]]></category>
		<category><![CDATA[Bug]]></category>
		<category><![CDATA[Query Optimizer]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=38</guid>
		<description><![CDATA[From time to time I have to fight against long parses. In this post I would like to share with you what happened to a customer of mine while upgrading from 9.2.0.7 to 10.2.0.3 (10.2.0.4 was not yet available at that time).
The parse of a complex SQL statement took 5 seconds in 9.2.0.7. Not very [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2008/08/long-parses/feed/</wfw:commentRss>
		<slash:comments>6</slash:comments>
		</item>
		<item>
		<title>Operation CONNECT BY WITH FILTERING</title>
		<link>http://antognini.ch/2008/06/operation-connect-by-with-filtering/</link>
		<comments>http://antognini.ch/2008/06/operation-connect-by-with-filtering/#comments</comments>
		<pubDate>Tue, 17 Jun 2008 09:09:57 +0000</pubDate>
		<dc:creator>Christian Antognini</dc:creator>
				<category><![CDATA[10gR1]]></category>
		<category><![CDATA[10gR2]]></category>
		<category><![CDATA[11gR1]]></category>
		<category><![CDATA[Bug]]></category>
		<category><![CDATA[Query Optimizer]]></category>
		<category><![CDATA[TOP]]></category>

		<guid isPermaLink="false">http://antognini.ch/?p=27</guid>
		<description><![CDATA[It happened to me several times to being asked about the mysterious full table scan in CONNECT BY operations. In this post I would like to share with you some of the information I wrote about it in my book (pages 233 to 236) .
The operation CONNECT BY WITH FILTERING is used to process hierarchical [...]]]></description>
		<wfw:commentRss>http://antognini.ch/2008/06/operation-connect-by-with-filtering/feed/</wfw:commentRss>
		<slash:comments>7</slash:comments>
		</item>
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