If you use ASM on a regular basis, you may find that knowledge of the internals can be very useful for advanced troubleshooting and in general to acquire familiarity with the technology. In particular this is even more relevant when using ASM capabilities for data redundancy/mirroring (i.e. when deploying disk groups with normal or high redundancy).
Databases at CERN blog
Topic: This post introduces the latest changes to OraLatencyMap and PyLatencyMap, two custom tools for collecting and displaying Oracle wait event latency details using heatmaps.
OraLatencyMap is a SQL*Plus tool, with a core written in PL/SQL, aimed at studying Oracle random I/O by displaying the latency drill-down of the wait event 'db file sequential read' using heatmaps. The tool can also be used to collect and display event latency histograms for any other Oracle wait event, for example: log file sync to study commit time latency.
In my previous blog post (http://db-blog.web.cern.ch/blog/szymon-skorupinski/2014-05-migrating-oracle-database-12c-what-do-auditing) I provided you with number of reasons why unified auditing looks very promising and should be seriously considered while migrating to 12c. Nonetheless, I was not talking at all about performance – which also seems to be greatly improved.
Topic: This post is about investigating the Oracle Optimizer using stack sampling and flame graphs. We will see how the complexity of the Optimizer has increased over the years and in particular with the introduction of cost-based optimization and more recently with 12c adaptive optimization.
Topic: This post is a hands-on introduction to using on-CPU Flame Graphs for investigating Oracle workloads. This technique is about collecting and visualizing sampled stack trace data to analyze and troubleshoot Oracle processes at the OS level (in particular applied to Linux).
Indexes… what indexes?
Indexes are one of the key Oracle features in terms of improving query performance and one might think it should be clear to everybody when and how to use them. Not at all... Working as a DBA for several years I was surprised to notice that so many developers do not know what indexes are, how they work and how to use them efficiently. I thought it would be good to put this knowledge down in a series of blog posts… and here we are! Let’s start with…
If you plan to introduce changes in your environment and want to estimate their impact, Real Application Testing feature seems to be one of the best options. As we needed to check the influence of changes planned in our databases, I've started to look for good candidates to capture the workloads. I wanted to capture only workloads associated with small number of schemas, but from several databases, to be able to properly simulate as much types of production workloads existing in our databases as possible.
If you consider migrating to Oracle Database 12c, no matter if you think of development, testing or production environments, one of many decisions you need to take is to define what to do with the auditing.
Topic: This blog entry is about investigating Oracle's DBMS_RESOURCE_MANAGER.CALIBRATE_IO
select 'Hello World' from dual@CERN;
Welcome to this new blog: “Databases at CERN, powering particle physics”. Why yet another blog?
The goal of this blog is to make the work around databases at CERN better known by sharing technical information to a wider audience. And who knows… it might trigger your interest in joining us for an internship, a fellowship or as a staff member.