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Checking out SQL Server via empirical data points
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I was reading Louis Davidson’s post earlier today, and what he said below caught my attention: “I am a big believer in having the database be as self contained as possible, so I try to put [maintenance] objects and such in the database, typically in a Read More...
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In my previous post on the performance impact of having a large number of virtual log files (VLFs) in a transaction log, I showed that a large number of VLFs could be very bad for SQL Server 2008 performance. The test workloads were large batch delete, Read More...
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It is generally known that having a large number of virtual log files (VLFs) in a database transaction log is undesirable. A blog post by the Microsoft support team in Stockholm showed that a large number of virtual log files could seriously lengthen Read More...
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Lies, damned lies, and statistics! If you have read my three previous posts ( 1 , 2 , 3 ), you may walk away with an impression that on a drive presented from a high-end enterprise class disk array, Windows file fragmentation does not have a significant Read More...
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There were discussions on disk misalignment on this site. See my previous post on “ Performance Impact of Disk Misalignment ”, and Kevin Kline’s blog on “ How to Improve Application and Database Performance up to 40% in One Easy Step ” But thanks to Jimmy Read More...
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What does it mean if you see a high percentage of signal waits? Thanks to Microsoft whitepapers, presentations, and blogs, everybody would say it implies CPU pressure. Well, almost everyone except Mario Broodbakker, whose excellent blog “ Taking the guesswork Read More...
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A frequently asked question is what counters should be included in a SQL Server baseline. The discussion then quickly proceeds to define a set of perfmon counters to be logged as the performance baseline. And often, people seem to have an urge to try Read More...
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To many, this is an old and tired topic, and any more mention of ad hoc queries versus parameterized queries may just send someone off the deep end. But recently I was doing some Oracle benchmarks, and the benchmark tool reported ~1,200 transactions per Read More...
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Microsoft publishes a list of so-called Common Engineering Criteria that its products should be compliant with. And this list is updated every year to keep up with the new technology and business development. Among the new criteria added this year, the Read More...
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Regardless of the DBMS make or model, the transaction throughput curve of a database system is often shaped like a trapezoid. As the load level goes up initially, so does the transaction throughput. As the load level continues to go up, the transaction Read More...
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In June 2006, Microsoft published a SQL Server technical paper on Physical Database Storage Design . This paper was updated in February 2007. The paper is generally well written, and the recommendations are reasonable. However, the following two specific Read More...
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Under the description for UPDATE in SQL Server 2000 and 2005 Books Online, you can find the following statement (thanks to SQL Server MVP Steve Kass for pointing me to this passage): The results of an UPDATE statement are undefined if the statement includes Read More...
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There has been much discussion on the usefulness of disk queue length as an indicator of a disk I/O bottleneck. Bob Dorr, for instance, addressed this issue directly in his excellent blog, SQL Server Urban Legends Discussed . But the issue is not settled Read More...
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The best documentation on the I/O behavior of SQL Server checkpoints is found in SQL Server 2000 I/O Basics by Bob Dorr. In particular, you should read the following carefully: SQL Server uses the following steps to set up another page for flushing and Read More...
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Within the SQL Server community, there is so much publicity on T-SQL set-oriented processing as good practice and the use of T-SQL cursors as bad practice that T-SQL cursors are effectively being seen as a plague to be avoided when in fact it's not the Read More...
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