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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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In response to my previous blog post-- Performance Impact: Setting a Database to Read Only , Shailesh Khanal mentioned that he observed significant performance degradation from READ COMMITTED SNAPSHOT OFF to ON for a read-only workload. This is counter Read More...
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Too many DBAs tend to view a drive presented from a Storage Area Network (SAN) as something of a monolithic nature. They look at the drive as if it had some intrinsic performance characteristics. This view doesn't help one appreciate the true performance Read More...
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With the insert script and the test configurations in my previous posts , the best data load throughput was 24GB in ~7 minutes when the checkpoint (and/or transaction commit) batch size was set to 100,000 ~ 1,000,000. That was the best result when I was Read More...
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In my previous posts ( 1 , 2 , 3 ), I focused on the performance behavior of setting the checkpoints and transaction commit sizes to once every 16 inserts and once every 100,000 inserts. A question remains: what is the most optimal size? In other words, Read More...
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In my two previous posts on the performance impact of frequent manual checkpoints and the I/O behavior of frequent manual checkpoints , I demonstrated that frequently issuing manual checkpoints can be bad for performance and why it's bad from the storage Read More...
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