A technical security analysis of the snmp daemon on Exadata

Recently I was asked to analyse the security impact of the snmp daemon on a recent Exadata. This system was running Exadata image version This blog article gives you an overview of a lot of the things that surround snmp and security.

First of all what packages are installed doing something with snmp? A list can be obtained the following way:

# rpm -qa | grep snmp
net-snmp-utils-5.5-54.0. (more...)

Conjuctive Normal Form

I recently tweeted about a comment I’d picked up at the Trivadis performance days regarding tablescans and performance.

“If you can write your SQL in conjunctive normal form it can help the optimizer to offload more predicates”

Inevitably someone asked me if I had an example to demonstrate this – I didn’t, and still don’t really, but here’s an interesting demo based on an example from the Oracle In-Memory blog showing how the optimizer will (more...)

OTN Appreciation Day: dbnodeupdate.sh

In the wake of the great hospitality shown by the OTN crew at Open World, Tim Hall thought that getting the community together for a series of “OTN appreciation” blogs would be a good way to show our thanks back.

Thinking about tools provided by Oracle that make my life easier, my mind went to dbnodeupdate.sh.  This tool helps automate many of the tedious tasks that must be performed when performing an OS update on an Exadata compute (more...)

How to enable Exadata Write-Back Flash Cache

Yes, this is well-known and the process has been described in Exadata Write-Back Flash Cache – FAQ (Doc ID 1500257.1) but what the note fails to make clear is that you do NOT have to restart cell services anymore hence resync the griddisks!

I had to enable the WBFC many times before and every time I’d restart the cell services, as note suggests. Well, this is not required anymore, starting with 11.2.3. (more...)

Extending an Exadata Eighth Rack to a Quarter Rack

In the past year I’ve done a lot of Exadata deployments and probably half of them were eighth racks. It’s one of those temporary things – let’s do it now but we’ll change it later. It’s the same with the upgrades – I’ve never seen anyone doing an upgrade from an eighth rack to a quarter. However, a month ago one of our customers asked me to upgrade their three X5-2 HC 4TB units from (more...)

Upgrade yourself from DBA to DMA

In any profession, learning never ends. From my very personal perspective and own exprience, I strongly beleinv in one who upgrade his skills always stays a step ahead from the rest. To stay competitive, it is necessary to upgrade our skills according the market demand.

For DBA folks who aim and dream to learn and upgrade their knwoledge with Oracle Exadata technologies, I wrote a 5 series article to Toad, below are the links to (more...)

You are in trouble when more than 8 kernel options are enabled in oracle executable

A brief headsup for everyone responsible for maintaining kernel options in the oracle executable.

The environment where I discovered this is a 3 node racattack cluster with Oracle GI & RDBMS After enabling Unified auditing in my database I noticed that all of a sudden database startup started failing with an almost  unlimited amount of core dump files being generated.

SQL*Plus: Release (more...)

addNode.sh, failed root.sh and IB listener

So this customer has an Exadata quarter rack and they have an IB listener configured on both DB nodes (for DB connections from a multi-racked Exalogic system). We were adding a new DB node to this rack. So just followed the standard procedure of creating users, directories etc on the new node, setting up ssh equivalence and running addNode.sh. All went fine but root.sh failed. Little looking into the logs revealed that it (more...)

How many memory is truly used by my Oracle instance?

There are many posts about the amount of memory that is taken by the Oracle database executables and the database SGA and PGA. The reason for adding yet another one on this topic is a question I recently gotten, and the complexities which surrounds memory usage on modern systems. The intention for this blogpost is to show a tiny bit about page sharing of linux for private pages, then move on to shared pages, and (more...)

OEDA–Things to keep an eye on

So if you are filling an OEDA for Exadata deployment there are few things you should take care of. Most of the screens are self explanatory but there are some bits where one should focus little more. I am running the Aug version of it and the screenshots below are from that version.

  1. On the Define customer networks screen, the client network is the actual network where your data is going to flow. So typically (more...)

Copy Data Management with Delphix on Exadata

I’ve been busy reading and testing everything I can with Delphix, whenever I get a chance.  I’m incredibly fascinated by copy data management and the idea of doing this with Exadata is nothing new, as Oracle has it’s own version with sparse copy.  The main challenge is that Exadata’s version of this is kind of clunky and really doesn’t have the management user interface that Delphix offers.


There (more...)

How to resolve missing dependency on exadata-sun-computenode-minimum

I’ve been really busy last few months – except spending a lot of time on M25 I’ve been doing a lot of Exadata installations and consolidations. I haven’t posted for some time now but the good news is that I got many drafts and presentations ideas.

This is a quick post about an issue I had recently. I had to integrate AD authentication over Kerberos on the compute nodes (blog post to follow) but had (more...)

SCAN Listener Crash After Applying July 2016 PSU

I ran in to a small issue while applying the July 2016 quarterly patch to a couple of Exadata racks last week.  The systems were running GI, previously with the January 2016 PSU.  The patches applied successfully, and we were beginning the process of running the post-patch scripts on the databases in the cluster.  This process involves manually starting the database in upgrade mode, and we saw a message in SQL*Plus that the (more...)

Redirecting ILOM Console Via SSH Tunneling With Putty

While preparing for a virtualized Exalytics upgrade, I was testing the various connection methods that would be needed.  Last on the list was to validate that I could connect to the ILOM’s web interface, launch the java console, and mount an ISO file from my laptop to the machine.   This is necessary because the Oracle VM server upgrade for a virtualized Exalytics requires you to boot from a specific ISO file in order to patch (more...)

ORA-15418: Appliance Mode Not Supported For Compatible.asm

The other day, I was upgrading a compatible.asm parameter to 12.1 on Exadata and I faced this error for the first time :

View the code on Gist.

Indeed, a diskgroup can have this parameter set to TRUE or FALSE :

View the code on Gist.

I then found this note on Metalink : EXADATA : What Is Oracle ASM appliance.mode Attribute (Doc ID 1664261.1) which explains that starting from Exadata (more...)

Notes on vendor lock-in

Vendor lock-in is an important subject. Everybody knows that. But few of us realize just how complicated the subject is, nor how riddled it is with paradoxes. Truth be told, I wasn’t fully aware either. But when I set out to write this post, I found that it just kept growing longer.

1. The most basic form of lock-in is:

  • You do application development for a target set of platform technologies.
  • Your applications can’t run (more...)

How To Configure Exadata Database Machine in Enterprise Manager Cloud Control 13c (OEM13c)

I have followed the steps in Oracle Documentation link: https://docs.oracle.com/cd/E63000_01/EMXIG/ch2_deployment.htm#EMXIG215 to configure Exadata Database Machine in OEM13c. If you want to configure your Exadata in OEM13c you have to follow the above mentioned link. In this post I will share the mandatory steps for configuration, and some of the issues which I faced while configuring the Exadata…

How To Avoid Exadata Cell Node Reboot While Modifying NTP Service

Recently, we had a hardware failure on our NTP server which caused its crash. Due to this, the ntpd daemon on compute nodes and cell nodes went offline. After fixing the hardware issue on NTP server, starting ntpd service using "service ntpd start" on compute nodes was successful but when I started the ntp service…

The Oracle database, in-memory parallel execution and NUMA

In a previous article called ‘memory allocation on startup’ I touched on the subject of NUMA; Non Uniform Memory Access. This article is about how to configure NUMA, how to look into NUMA usage and a real life case of NUMA optimisation using in-memory parallel execution.

At this point in time (start of the summer of 2016) we see that the CPU speed competition has stagnated and settled at somewhere below maximally 4 gigahertz, and (more...)

ORA-56841: Master Diskmon cannot connect to a CELL

Faced this error while querying v$asm_disk after adding new storage cell IPs to cellip.ora on DB nodes of an existing cluster on Exadata. Query ends with ORA-03113 end-of-file on communication channel and ORA-56841 is reported in $ORA_CRS_HOME/log/<hostname>/diskmon/diskmon.log. Reason in my case was that the new cell was using different subnet for IB. It was pingable from the db nodes but querying v$asm_disk wasn’t working. Changing the subnet for IB on new cell to (more...)