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	<title>The Pythian Blog &#187; Riyaj Shamsudeen</title>
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		<title>Performance tuning: HugePages in Linux</title>
		<link>http://www.pythian.com/news/1326/performance-tuning-hugepages-in-linux/</link>
		<comments>http://www.pythian.com/news/1326/performance-tuning-hugepages-in-linux/#comments</comments>
		<pubDate>Mon, 10 Nov 2008 19:38:32 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Oracle]]></category>
		<category><![CDATA[hugepages]]></category>
		<category><![CDATA[Linux]]></category>
		<category><![CDATA[memlock]]></category>
		<category><![CDATA[page table]]></category>
		<category><![CDATA[performance]]></category>
		<category><![CDATA[sar]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/1326/performance-tuning-hugepages-in-linux</guid>
		<description><![CDATA[Recently we quickly and efficiently resolved a major performance issue with one of our New York clients. In this blog, I will discuss about this performance issue and its solution. Problem statement The client&#8217;s central database was intermittently freezing because of high CPU usage, and their business severely affected. They had already worked with vendor [...]]]></description>
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		<slash:comments>18</slash:comments>
		</item>
		<item>
		<title>Riyaj&#8217;s Presentations at SIOUG and DOUG</title>
		<link>http://www.pythian.com/news/1330/riyajs-presentations-at-sioug-and-doug/</link>
		<comments>http://www.pythian.com/news/1330/riyajs-presentations-at-sioug-and-doug/#comments</comments>
		<pubDate>Mon, 03 Nov 2008 20:06:30 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Non-Tech Articles]]></category>
		<category><![CDATA[Oracle]]></category>
		<category><![CDATA[DOUG]]></category>
		<category><![CDATA[papers]]></category>
		<category><![CDATA[Portoroz]]></category>
		<category><![CDATA[presentations]]></category>
		<category><![CDATA[SIOUG]]></category>
		<category><![CDATA[UKOUG]]></category>
		<category><![CDATA[Venice]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/1330/riyajs-presentations-at-sioug-and-doug</guid>
		<description><![CDATA[I recently traveled to Europe to present at a few conferences. The Slovenia Oracle User Group (SIOUG) conducted an Oracle conference in Portoroz, a port city in Adriatic Sea. Thanks to my friend Joze Senegacnik, I had wonderful time in Slovenia. We also visited the city of Venice while we were there. Of course, we [...]]]></description>
		<wfw:commentRss>http://www.pythian.com/news/1330/riyajs-presentations-at-sioug-and-doug/feed/</wfw:commentRss>
		<slash:comments>3</slash:comments>
		</item>
		<item>
		<title>Oracle Performance Issue: High Kernel-Mode CPU Usage</title>
		<link>http://www.pythian.com/news/1324/oracle-performance-issue-high-kernel-mode-cpu-usage/</link>
		<comments>http://www.pythian.com/news/1324/oracle-performance-issue-high-kernel-mode-cpu-usage/#comments</comments>
		<pubDate>Thu, 30 Oct 2008 17:58:28 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Oracle]]></category>
		<category><![CDATA[ccNUMA]]></category>
		<category><![CDATA[numa]]></category>
		<category><![CDATA[performance]]></category>
		<category><![CDATA[RAC performance myths]]></category>
		<category><![CDATA[scientific tuning]]></category>
		<category><![CDATA[shmdt]]></category>
		<category><![CDATA[_db_block_numa]]></category>
		<category><![CDATA[_enable_numa_optimization]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/1324/oracle-performance-issue-high-kernel-mode-cpu-usage</guid>
		<description><![CDATA[Recently, I resolved a performance issue with one of our esteemed clients. I found the problem interesting and worth blogging about. The problem An application makes 300 static connections to database DB1 in the database server, say CLNTDB server. The application relies on database link and over a period of time, each session executes SQL [...]]]></description>
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		<slash:comments>2</slash:comments>
		</item>
		<item>
		<title>How to Find Objects Creating nologging Changes</title>
		<link>http://www.pythian.com/news/1209/how-to-find-objects-creating-nologging-changes/</link>
		<comments>http://www.pythian.com/news/1209/how-to-find-objects-creating-nologging-changes/#comments</comments>
		<pubDate>Thu, 04 Sep 2008 19:44:09 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Oracle]]></category>
		<category><![CDATA[internals]]></category>
		<category><![CDATA[nologging]]></category>
		<category><![CDATA[redo logging]]></category>
		<category><![CDATA[standbys]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/1209/how-to-find-objects-creating-nologging-changes</guid>
		<description><![CDATA[In an Oracle-l thread, this question was raised: how can you find objects creating nologging changes? First, what is a &#8216;nologging&#8217; change? The redo logging mechanism plays critical role in media recovery. Media recovery relies on archivelog files generated to roll the database forward. A standby database or dataguard recovery also relies on archivelog files. [...]]]></description>
		<wfw:commentRss>http://www.pythian.com/news/1209/how-to-find-objects-creating-nologging-changes/feed/</wfw:commentRss>
		<slash:comments>1</slash:comments>
		</item>
		<item>
		<title>Oracle Import Performance: Does Import Use Single-Row Inserts for Date Columns?</title>
		<link>http://www.pythian.com/news/1157/oracle-import-performance-does-import-use-single-row-inserts-for-date-columns/</link>
		<comments>http://www.pythian.com/news/1157/oracle-import-performance-does-import-use-single-row-inserts-for-date-columns/#comments</comments>
		<pubDate>Tue, 05 Aug 2008 20:04:24 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Oracle]]></category>
		<category><![CDATA[buffer]]></category>
		<category><![CDATA[clob]]></category>
		<category><![CDATA[date]]></category>
		<category><![CDATA[import performance]]></category>
		<category><![CDATA[tkprof]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/1157/oracle-import-performance-does-import-use-single-row-inserts-for-date-columns</guid>
		<description><![CDATA[Recently, I was involved in a discussion about import performance in this OTN forum in which the original poster raised the issue of whether or not import will resort to single-row inserts for tables with date columns. For array inserts, the buffer parameter essentially specifies the size of this array. We know, however, that if [...]]]></description>
		<wfw:commentRss>http://www.pythian.com/news/1157/oracle-import-performance-does-import-use-single-row-inserts-for-date-columns/feed/</wfw:commentRss>
		<slash:comments>4</slash:comments>
		</item>
		<item>
		<title>Tuning Latch Contention: Cache-buffers-chain latches</title>
		<link>http://www.pythian.com/news/1135/tuning-latch-contention-cache-buffers-chain-latches/</link>
		<comments>http://www.pythian.com/news/1135/tuning-latch-contention-cache-buffers-chain-latches/#comments</comments>
		<pubDate>Fri, 25 Jul 2008 20:24:55 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Oracle]]></category>
		<category><![CDATA[buffer chain latches]]></category>
		<category><![CDATA[latch contention]]></category>
		<category><![CDATA[tuning]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/1135/tuning-latch-contention-cache-buffers-chain-latches</guid>
		<description><![CDATA[Recently, I had an opportunity to tune latch contention for cache buffers chain (CBC) latches. The problem was high CPU-usage combined with poor application performance. A quick review of the statspack report for 15 minutes showed a latch-free wait as the top event, consuming approximately 3600 seconds in an 8-CPU server. CPU usage was quite [...]]]></description>
		<wfw:commentRss>http://www.pythian.com/news/1135/tuning-latch-contention-cache-buffers-chain-latches/feed/</wfw:commentRss>
		<slash:comments>16</slash:comments>
		</item>
		<item>
		<title>Tuning &#8216;log file sync&#8217; Event Waits</title>
		<link>http://www.pythian.com/news/1098/tuning-log-file-sync-event-waits/</link>
		<comments>http://www.pythian.com/news/1098/tuning-log-file-sync-event-waits/#comments</comments>
		<pubDate>Fri, 27 Jun 2008 21:26:36 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Oracle]]></category>
		<category><![CDATA[LGWR]]></category>
		<category><![CDATA[log file sync]]></category>
		<category><![CDATA[performance]]></category>
		<category><![CDATA[root cause analysis]]></category>
		<category><![CDATA[tuning]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/1098/tuning-log-file-sync-event-waits</guid>
		<description><![CDATA[In this blog entry, I will discuss strategies and techniques to resolve &#8216;log file sync&#8217; waits. This entry is intended to show an approach based upon scientific principles, not necessarily a step-by-step guide. Let&#8217;s understand how LGWR is inherent in implementing the commit mechanism first. Commit Mechanism and LGWR Internals At commit time, a process [...]]]></description>
		<wfw:commentRss>http://www.pythian.com/news/1098/tuning-log-file-sync-event-waits/feed/</wfw:commentRss>
		<slash:comments>19</slash:comments>
		</item>
		<item>
		<title>Resolving High Water Enqueue Contention</title>
		<link>http://www.pythian.com/news/1008/resolving-hw-enqueue-contention/</link>
		<comments>http://www.pythian.com/news/1008/resolving-hw-enqueue-contention/#comments</comments>
		<pubDate>Wed, 21 May 2008 16:43:32 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Oracle]]></category>
		<category><![CDATA[Oracle E-Business Suite]]></category>
		<category><![CDATA[enqueue]]></category>
		<category><![CDATA[high water]]></category>
		<category><![CDATA[high water mark]]></category>
		<category><![CDATA[HW]]></category>
		<category><![CDATA[HWM]]></category>
		<category><![CDATA[_bump_highwater_mark_count]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/1008/resolving-hw-enqueue-contention</guid>
		<description><![CDATA[Recently, I had a few email exchanges &#8212; on the Oracle-l list and offline &#8212; about HW enqueue contention. A few interesting observations emerged from test cases I created during that discussion. HW Enqueue When a session needs access to a resource, it requests a lock on that resource in a specific mode. Internally, lock [...]]]></description>
		<wfw:commentRss>http://www.pythian.com/news/1008/resolving-hw-enqueue-contention/feed/</wfw:commentRss>
		<slash:comments>3</slash:comments>
		</item>
		<item>
		<title>Identifying SQL Execution Bottlenecks Scientifically</title>
		<link>http://www.pythian.com/news/937/identifying-sql-execution-bottlenecks-scientifically/</link>
		<comments>http://www.pythian.com/news/937/identifying-sql-execution-bottlenecks-scientifically/#comments</comments>
		<pubDate>Wed, 23 Apr 2008 16:34:47 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Oracle]]></category>
		<category><![CDATA[bottlenecks]]></category>
		<category><![CDATA[statistics_level]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/937/identifying-sql-execution-bottlenecks-scientifically</guid>
		<description><![CDATA[A few days ago, a developer and I had an interesting conversation. The developer was trying to tune an expensive SQL statement, using following trial-and-error method: loop until acceptable performance explain plan -&#62; execute SQL with sql trace -&#62; tkprof -&#62; rewrite end loop; After looking at his method in amusement, I showed him how [...]]]></description>
		<wfw:commentRss>http://www.pythian.com/news/937/identifying-sql-execution-bottlenecks-scientifically/feed/</wfw:commentRss>
		<slash:comments>2</slash:comments>
		</item>
		<item>
		<title>Multi-Column Correlation and Extended Stats in Oracle 11g</title>
		<link>http://www.pythian.com/news/906/multi-column-correlation-and-extended-stats-in-oracle-11g/</link>
		<comments>http://www.pythian.com/news/906/multi-column-correlation-and-extended-stats-in-oracle-11g/#comments</comments>
		<pubDate>Wed, 09 Apr 2008 18:35:51 +0000</pubDate>
		<dc:creator>Riyaj Shamsudeen</dc:creator>
				<category><![CDATA[Group Blog Posts]]></category>
		<category><![CDATA[Oracle]]></category>
		<category><![CDATA[Oracle E-Business Suite]]></category>
		<category><![CDATA[11g]]></category>
		<category><![CDATA[cbo]]></category>
		<category><![CDATA[extended stats]]></category>
		<category><![CDATA[sys_op_combined_hash]]></category>

		<guid isPermaLink="false">http://www.pythian.com/blogs/906/multi-column-correlation-and-extended-stats-in-oracle-11g</guid>
		<description><![CDATA[We all have encountered this situation many times before: the cost-based optimizer assumes no correlation between two columns (until 11g), and this has the effect of erroneously reducing the cardinality of a row source. Incorrect cardinality estimates are one of many root causes for SQL performance issues. Consider the following example. This code creates a [...]]]></description>
		<wfw:commentRss>http://www.pythian.com/news/906/multi-column-correlation-and-extended-stats-in-oracle-11g/feed/</wfw:commentRss>
		<slash:comments>5</slash:comments>
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