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Printing system call arguments in gdb

This blogpost is about how to print the system call arguments of a system call which is caught with ‘catch’ or ‘break’ in gdb. The reason for this blogpost is I spend quite some time on searching for this, and working around this, so writing it in a blogpost might help others who spend (some of) their time in the gdb debugger, and encounter the same issue.

When you break on a system call in gdb, it will show you something like this:

Getting up and running with UCP and Application Continuity

I have already posted a couple of articles on the use of Oracle’s Universal Connection Pool in the past with regards to Workload Management and Oracle RAC 11.2. Since then a lot happened, with the release of Oracle 12c being the most notable event. With 12c you get lots of interesting new features for JDBC, and the one I would like to present today is Application Continuity. This continues the previous post on playing with Application Continuity outside of a midlle-tier environment. Well, if you allow me to call Tomcat 7 “middle-tier” that is.

The aim of this post is to extend my previous posts about setting up UCP with Application Continuity. The basic setup remains unchanged, but this time I tested with JDK 1.6 (build 1.6.0_45-b06) and Tomcat 7.0.47 on Oracle Enterprise Linux 6.4 64bit.

When the Oracle wait interface isn’t enough, part 2: understanding measurements.

In my blogpost When the oracle wait interface isn’t enough I showed how a simple asynchronous direct path scan of a table was spending more than 99% of it’s time on CPU, and that perf showed me that 68% (of the total elapsed time) was spent on a spinlock unlock in the linux kernel which was called by io_submit().

This led to some very helpful comments from Tanel Poder. This blogpost is a materialisation of his comments, and tests to show the difference.

First take a look at what I gathered from ‘perf’ in the first article:

Building vmware-tools in your Oracle Linux UEK3 VM

This is a quick writeup of an oddity I found while trying to install the vmwareware tools in an Oracle Linux host with the UEK3 kernel enabled (which is by default).

This is what is encountered during the vmware tools installation dialog when running vmwaretools.pl:

Searching for a valid kernel header path...
The path "" is not a valid path to the 3.8.13-16.2.2.el6uek.x86_64 kernel 
headers.
Would you like to change it? [yes]

The building of vmware tools fail because the kernel headers can not be found: the installer doesn’t see the kernel headers, whilst you probably installed it (it’s the kernel-uek-devel package belonging to the running kernel).

Playing with Application Continuity in RAC 12c

One of the more interesting features in Oracle 12c RAC is application continuity. Why do I believe it is? Because it relieves developers from having to think about retrying connections and catch SQLExceptions in the code. I already thought that Fast Application Notification and Fast Connect Failover (FCF) are great, _but_ they required the developer to understand RAC and Oracle which you can’t take for granted. In fact looking back over the last few years since I co-wrote Pro Oracle Database 11g RAC on Linux the number 1 complaint I got from developers was that RAC was too complex (see for example in this thread on oracle-l)

Now Application Continuity takes away 2 problems I have seen.

Be aware of these environment variables in .bashrc et al.

This is a quick post about one of my pet peeves-statically setting environment variables in .bashrc or other shell’s equivalents. I have been bitten by this a number of times. Sometimes it’s my own code, as in this story.

Background

Many installation instructions about Oracle version x tell you to add variables to your shell session when you log in. What’s meant well for convenience can backfire. Sure it’s nice to have ORACLE_HOME, ORACLE_SID, LD_LIBRARY_PATH, CLASSPATH etc set automatically without having to find out about them the hard way. However, there are situations where this doesn’t help.

Upgrading to Oracle Linux 6.5

This is a very short post to demonstrate how to upgrade to Oracle Linux 6.5. My lab system was reasonably current, Oracle Linux 6.4 with some security patches (but not all). The upgrade to 6.5 (or “latest”) is very simple, and since Oracle announced they had beefed up connectivity it’s a real joy. Instead of 450kb/s I get around 9 MB/s. For those of you who want the ISO image: you can’t currently get it from edelivery, the only update method is YUM/ULN or you download the ISO from My Oracle Support, patch 17860279.

Hard Drive Predictive Failures on Exadata

This post also applies to non-Exadata systems as hard drives work the same way in other storage arrays too – just the commands you would use for extracting the disk-level metrics would be different.

I just noticed that one of our Exadatas had a disk put into “predictive failure” mode and thought to show how to measure why the disk is in that mode (as opposed to just replacing it without really understanding the issue ;-)

Inside a RAC 12c GNS cluster

Based on some reader feedback I started looking at GNS again, but this time it will be for RAC 12c. According to the documentation GNS has been enhanced so that you can use it without subdomain delegation. I decided to try the “old fashioned” way though: DHCP for VIPs, SCAN IPs, subdomain delegation and the like as it is the most complex setup. I occasionally like complex.

The network setup is exactly the same as I used before in 11.2 and thankfully didn’t require any changes. The cluster I am building is a 2 node system on Oracle Linux 6.4 and the Red Hat compatible kernel. I have to use this as the Unbreakable Kernel doesn’t know about block devices made available to it via virtio-scsi. I use virtio-scsi for shared block devices very much in the same way I did for Xen.

Drill Down the I/O stack at UKOUG Tech13

It's just under a week to go before the doors open for the UKOUG Tech13 conference and the adjoining OakTable World UK 2013 sessions, so I thought I would write a very short blog post about what I will be doing there, where I'll be, and what I'm looking forward to. This year I will […]