I have seen several clients who are struggling to decode page allocation failures on Exadata, in this post i will try to explain how to read the backtrace. The following is an anonymized client case where page allocation failures are leading up to a node reboot.
Jan 1 11:58:02 dm01db01 (more...)
An Oracle Exadata Full Rack consists of 8 DB compute nodes. Oracle has shifted the strategy to patching the exadata in 220.127.116.11.0 onwards to using Yum as the method of patching. the Quarterly Full Stack does not include the DB Compute nodes patches anymore. So that (more...)
I’ll be co-speaking with Tyler Muth at E4 and we will be talking about Performance Visualization… some of you may already know that I’m really a big fan of Tableau and just to give you an example on what the tool can do I’ve consolidated all the different viz that (more...)
The basic idea behind the Exadata Hybrid Columnar Compression (hereby referred as EHCC) is to reprise the benefits of column based storage while sustaining to the fundamental row based storage principle of Oracle database. Oftentimes the databases following column based storage claim that comparatively they needs less IO to retrieve (more...)
I have announced my webinar on Oracle ZFS Storage Appliance for Exadata Backup & Recovery in NYOUG DBA webinar series. You can download webinar slides and voice recod from NYOUG web site
In Friday December 14, 2012 at 12:00 PM -1:00 PM EDT I will be giving a webinar for NYOUG SIG with the following abstract
When it comes to the backup and recovery infrastructure of the Exadata Database Machine, conventional solutions often have only limited performance to keep up with Exadata throughput, whereas Oracle ZFS Storage Appliance can be configured as a very fast, capable, and easy-to-manage backup and recovery solution for any Exadata environment. In this session Husnu Sensoy will describe some of the configuration possibilities of the ZFS Storage Appliance to create a flexible backup and recovery environment for Exadata, (more...)
I’ve been working a lot with graphing DB and OS metrics in R. I find it especially useful in Exadata POVs (proof of value) to gather and graph the oswatcher vmstat files for the compute nodes and iostat for the cells. For an example, take a look at this graph (PDF, 168 KB) of what [...]
With the announcement Exadata X3, Oracle has introduced a new feature called “FlashCache Writeback” to allow writes to cell Flash Cache (aka Exadata Smart FlashCache) in WriteBack mode. Earlier with WriteThrough mode, writes were not written to FlashCache, instead they were written directly to cell disks. Exadata software used to decide whether to cache these writes back into FlashCache or not. In WriteBack mode, writes are written to cell FlashCache and acknowledgement is given back to calling process as soon as data is written to flashcache. Exadata Server software de-stages the dirty writes in flashcache to spinning disks in the (more...)
In my last post, I looked at the effect of the Exadata smart flash logging. Overall, there seemed to be a slight negative effect on median redo log sync times. This chart (slightly different from the last post because of different load and configuration of the system), shows how there’s a “hump” of redo log syncs that take slightly longer when the flash logging is enabled:
But of course, the flash logging feature was designed to improve performance not of the “average” redo log sync, but of the “outliers”.
In my tests, I had 40 concurrent (more...)
Just a quick note about change in the way the compute nodes are patched starting from version 18.104.22.168.1. For earlier versions Oracle provided the minimal pack for patching the compute nodes. Starting with version 22.214.171.124.1 Oracle has discontinued the minimal pack and the updates to compute nodes are done via Unbreakable Linux Network (ULN).
Now there are three ways to update the compute nodes:
1) You have internet access on the Compute nodes. In this case you can download patch 13741363, complete the one time setup and start the update.
I’ll be speaking at the Enkitec Extreme Exadata Expo (E4), August 13-14 in Dallas Texas (you can also attend virtually). They’ve recruited some of the top names from community including keynote speaker Andrew Mendelsohn, Arup Nanda, Cary Millsap, Jonathan Lewis, Karen Morton, Maria Colgan, Kerry Osborne and Tanel Põder. I left a lot of names off the list, many of which you probably [...]
I’ll be co-speaking with Randy Johnson (one of the authors of Expert Oracle Exadata) at E4 to share about the war stories and detail on a bunch of technical stuff on a Peoplesoft and BIEE consolidation project we had on one of our clients. See the abstract below:
Randy Johnson & Karl Arao
A PeopleSoft & OBIEE Consolidation Success Story
In today’s competitive business climate companies are under constant pressure to reduce costs without sacrificing quality. Many companies see database and server consolidation as the key to meeting this goal. Since its introduction, Exadata has become the obvious choice for (more...)
Last week I had a lengthy post at oracle-l that tackles Calibrate IO, Short Stroking, Stripe size, UEK kernel, and ASM redundancy effect on IOPS Exadata which you can read here
followed by interesting exchange of tweets with Kevin Closson here (see 06/21-22 tweets) which I was replying in between games at UnderwaterHockey US Nationals 2012 which we won the championship for the B division I have my awesome photo with the medal here
This post will detail on the ASM redundancy/parity effect on IOPS… if… by changing the ASM redundancy (external, normal, and high) will it decrease the workload (more...)
Tuning has always being good fun and something like a challenge for me.
From time to time we are being asked to find out why something did run slow while you are sleeping; answering this question is, in most cases, a challenge.
My batch did run slow last night, can you let us know why? Or why did this query run slow? Are questions we, as DBAs, have to answer from time to (more...)
I’ve seen some posts on the blogosphere where people attempt to explain (or should I say guess) how Exadata Smart Flash Logging works and most of them are wrong. Hopefully this post will help clear up some the misconceptions out there.
The following is an excerpt from the paper entitled “Exadata Smart Flash Cache Features and the Oracle Exadata Database Machine” that goes into technical detail on the Exadata Smart Flash Logging feature.
Smart Flash Logging works as follows. When receiving a redo log write request, Exadata will do
parallel writes to the on-disk redo logs as well (more...)
From time to time, I have to run scripts or single commands on all nodes for Exadata. This can take some time.
We have a request from our developers to flush the shared pool on all nodes on our UAT Exadata. This is due to a bug we are still experiencing.
This is a typical request for my team, were we have to run something on all our nodes. Flushing shared pool can be one of them.
Connecting and executing the same command 8 times, if you have a full rack, can be time-consuming and it (more...)