Recently we were refreshing our recovery system infrastructure, by moving automatic recoveries to new servers, with big bunch of disks directly connected to each of them. Everything went fine until we started to run recoveries - they were much slower than before, even though they were running on more powerful hardware. We started investigation and found some misconfigurations, but after correcting them, performance gain was still too small.
Databases at CERN blog
Sneak peek into the life as a CERN Openlab Summer Student
It was a mix of bewilderment and awe when the first email came declaring that I was selected for the Openlab Summer Student Program. Little did I know that the journey would end in a mix of sadness (I never wanted to come back) and infinite memories (intricacies that even pictures cannot capture.)
A little bit scary title, isn't it? Please keep in mind that definitely it is neither supported nor advised method to solve your problems and you should be really careful while doing it - hopefully not on production environment. But it may sometimes happen that you end up with the situation where creating your own merge patch for Oracle database could not be as crazy idea as it sounds :).
Topic: this post is about some simple tools and techniques that can be used to drill down high-latency I/O events using SystemTap probes.
Topic: This post is about collecting and visualizing I/O latency histograms for NetApp filers in C-mode.
Regular readers of our blog probably already know that for most of our databases we're using two storage layers to keep our backups - NAS volumes as a primary layer and tapes as secondary one - please check "Datafile without backups - how to restore?" for more details. If you read another post "Importance of testing yours ba
Topic: event histogram metric, a script and some related discussions on collecting and displaying wait event latency histograms for Oracle performance troubleshooting.
CHEP 2015, the 21st international conference on computing in high energy physics, has taken place in April 2015 in Okinawa, Japan. Here below you can find the links to the pdf of the talks, posters and related preprints of two of the contributions by members the CERN database group. These are on the topics of our tests with scale-out databases (in particular on the Hadoop platform) and on the evolution of the replication technologies used for our Oracle databases (our use of Streams, GoldenGate and Active Data Guard):
Oracle Managed Files (OMF) have many advantages, but the fact that such files could coexist in the same database with manually added (and named) ones, could sometimes lead to confusion. Situation is made worse by the fact, that there is no straightforward way (at least of which I'm aware of...or rather was - please check the comment of Mikhail Velikikh) to say if the file is Oracle managed or not. Oracle documentation seems to confirm this: