Tag: performance

High System Time on Windows Running in a VM

Recently I’ve seen an issue with CPU usage on a server running Windows 2003 Server in a VMware. This is a small Virtual Machine with just 2 cores allocated (which are possibly mapped to “threads” on a host level but…

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In-Memory Column Store: 10046 May Be Lying to You!

The Oracle In-Memory Column Store (IMC) is a new database option available to Oracle Database Enterprise Edition (EE) customers. It introduces a new memory area housed in your SGA, which makes use of the new compression functionality brought by the…

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Comparing CPU Throughput of Azure and AWS EC2

After observing CPU core sharing with Amazon Web Services EC2, I thought it would be interesting to see if Microsoft Azure platform exhibits the same behavior. Signing up for Azure’s 30-day trial gives $200 in credit to use over the…

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vCPU sharing in EC2: HVM to the rescue?

I’ve been doing some testing to clarify what a vCPU in Amazon Web Services actually is. Over the course of the testing, I experienced inconsistent results on a 2-thread test on a 4-vCPU m3.xlarge system, due to the mislabeling of…

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Virtual CPUs with Amazon Web Services

The definition of a vCPU in Amazon Web Services is a bit unclear. We run some tests to see how much CPU performance we actually get, and discover some unexpected side effects from AWS’s implementation.

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SQL Server Statistics: Maintenance and Best Practices

What are Statistics? There are multiple paths a database can use to answer a query, some of them being faster and more efficient than others. It is the job of the query optimizer to evaluate and choose the best path,…

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Do AWR Reports Show the Whole Picture?

AWR report is a great source of aggregated information on top activities happening in our databases. I use data collected in AWR quite often, and obviously the easiest way of getting the data out from the AWR is by running the…

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Do you have enough Redo?

The question of whether a database has enough redo logs available is quite common. The documentation suggests to use FAST_START_MTTR_TARGET and V$INSTANCE_RECOVERY.OPTIMAL_LOGFILE_SIZE to identify “the optimal” redo log size based on the target recovery time. I’ve never used it and…

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Batched Table Access

When I first saw the suffix BATCHED in an Oracle execution plan from 12c, I was curious to see what is hidden behind and how it works. I had some spare time for testing and wanted to share my findings…

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Mining the AWR to Identify Performance Trends

Sometimes it’s useful to check how performance of a SQL statement changes over time. The diagnostic pack features provide some really useful information to answer these questions. The data is there, but it not always easy to retrieve it, especially if…

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