Topic: This blog post is about kernel stack profiling and visualization with flame graphs.
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.
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.
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:
I've already described how important is to test your backup strategy and restore/recovery procedures, but while doing so, you could of course encounter some problems, not really related with the recoverability as such. Recently, we've got such a problem on our recovery server, at the very beginning of an automatic restore (database name masked):
Topic: PyLatencyMap v1.2 a tool for collecting and visualizing I/O latency data collect
Since version 11.1 of Oracle database, there is very useful command available, allowing DBAs to easily move RMAN recovery catalog schemas between databases. Its functionality is even broader, as it also allows one catalog schema to be merged into another - either the whole schema or just the metadata of chosen databases. Command I'm writing about is of course import catalog, which I had a chance to use recently, to move our recovery catalog to the new database.
Have you ever had a problem with restoring datafiles without any backups available? It's easy, of course if you have all archived logs from the time datafile was created. Please check it here: Re-Creating Data Files When Backups Are Unavailable. Moreover, RMAN is clever enough to create empty datafile automatically during restore phase and then recover it using archived logs. So far, so good, but...
Topic: This post is about tracing logical and physical reads in Oracle using SystemTap. You find here a few examples illustrating the main mechanisms used by Oracle to performo physical and logical I/O and you learn how to build SystemTap scripts to further explore and troubleshoot Oracle I/O.
The views expressed in this blog are those of the authors and cannot be regarded as representing CERN’s official position.
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