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Clemens Bleile

CPUs: Cores versus Threads on an Oracle Server

By | Database Administration & Monitoring, Database management, Oracle | 4 Comments

When doing a performance review I often do talk with the DBA about the CPU utilization of the server. How reliable is the server CPU utilization with tools like top or the host CPU utilization in the AWR-report? E.g. on an Linux Intel x86-64 server with 8 Cores and 16 logical CPUs (Intel Hyperthreading), what does a utilization of 50% mean? As I had an ODA X7-M in a test lab available, I thought I’ll…

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Microsoft Team

Index seek operator and residual IO

By | Database Administration & Monitoring | No Comments

This blog post draws on the previous article about index seek and gotchas. I encountered another interesting case but it is not so much because of the nature of the problem I decided to write this article but rather the different ways that exist to troubleshoot it. Firstly, let’s set the scene: A simple update query and its corresponding execution plan that tend to say the plan is efficient  in terms of performance declare @P0…

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Microsoft Team

Experiencing update statistics on a big table with circuitous ways

By | Database Administration & Monitoring | No Comments

This is my first blog of this new year and since a while by the way. Indeed, last year, I put all my energy to realign my Linux skills with the new Microsoft’s strategy that opens SQL Server to Open Source world. But at the same time, I did a lot of interesting stuff at customers shops and I decided to write about one  of them to begin this new year 2018. In this blog…

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Microsoft Team

SQL Server 2016: distributed availability groups and cascaded replicas

By | Database Administration & Monitoring | No Comments

During the last MVP summit, we had some interesting discussions about availability groups with the SQL Server team and I remember someone asked for managing scenarios like Oracle cascaded destinations and the good news is that SQL Server 2016 already addresses this kind of scenario with distributed availability groups. For example, let’s say you have to manage heavily reporting activity on your application and a solution would be to offload this activity across several secondary…

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Microsoft Team

SQL Server AlwaysOn availability groups and statistic issues on secondaries

By | Database Administration & Monitoring | 9 Comments

I would like to share with you an interesting issue you may face while using SQL Server AlwaysOn availability groups and secondary read-only replicas. For those who use secondary read-only replicas as reporting servers, keep reading this blog post because it is about update statistics behavior on the secondary replicas and as you may know cardinality estimation accuracy is an important part of the queries performance in this case. So a couple of days ago,…

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Microsoft Team

Partitioning – When data movement is not performed as expected

By | Database Administration & Monitoring | No Comments

This blog is about an interesting partitioning story and curious data movements during merge operation. I was at my one of my customer uses intensively partitioning for various reasons including archiving and manageability. A couple of days ago, we decided to test the new fresh developed script, which will carry out the automatic archiving stuff against the concerned database in quality environment. Let’s describe a little bit the context. We used a range-based data distribution…

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Microsoft Team

When an index seek operator is not always your friend

By | Development & Performance | No Comments

Did you ever consider an index seek as an issue? . Well, let’s talk about a story with one of my customers where the context is pretty simple: a particular query that is out of the range of the application’s performance requirements (roughly 200ms of execution time in average). The execution plan of the query was similar to what you may see in the picture below:   At first glance, no obvious way to improve…

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Microsoft Team

SQL Server AlwaysOn: troubleshooting improvements with new service packs

By | Database Administration & Monitoring | No Comments

As promised in my latest blog, I will talk about improvements in the detection of the availability group replication latency. As a reminder, replication latency between high available replicas may be monitored in different manners so far. Firstly, in my experience I had the opportunity to use different performance counters as “Database Replica:Transaction Delay” and “Databas Replica:Mirrored Write Transactions/sec” in order to get a good picture of the latency over the time after implementing an…

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Microsoft Team

SQL Server 2016 AlwaysOn: Direct seeding and performance considerations

By | Database Administration & Monitoring, Development & Performance | No Comments

This blog post follows the previous one about new direct seeding feature shipped with SQL Server 2016. As a reminder, I had some doubts about using direct seeding with large databases because log stream is not compressed by default but I forgot the performance improvements described into the Microsoft BOL. I also remembered to talk about it a couple of months ago in this blog post. So let’s try to combine all the things with the…

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Microsoft Team

SQLSaturday #510–Locks, latches et spinlocks

By | Technology Survey | No Comments

J-16 avant le prochain SQL Saturday Ă  Paris et il est encore temps de s’inscrire.  Le prochain SQL Saturday en quelques chiffres c’est: 4 parcours 20 sessions + Chalk-Talk 9 nationalitĂ©s 15 speakers francophones 10 speakers anglophones de rĂ©putation internationale En rĂ©sumĂ© un Ă©vĂ©nement Ă  ne pas louper! Pour ma part j’aurais l’opportunitĂ© de parler du verrouillage logique et physique sous SQL Server (dernière session de la journĂ©e). En guise d’appetizer: dĂ©bogage de problèmes de latch…

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