New option for configuring multipathing in Oracle Linux 7

Teaching is and remains the best way for picking up new things :) While updating notes for a class I came across an interesting change in the way the device-mapper multipath works in Oracle Linux 7.4.

In the past, everyone including me used scsi_id to get the WWID of a LUN for use with dm-multipath. This is still the way Oracle documents it for Oracle Linux 7.

The utility was specified as an argument (more...)

A look into oracle redo, part 9a: commit – concurrency considerations

During the investigations of my previous blogpost about what happens during a commit and when the data becomes available, I used breaks in gdb (GNU debugger) at various places of the execution of an insert and a commit to see what is visible for other sessions during the various stages of execution of the commit.

However, I did find something else, which is very logical, but is easily overlooked: at certain moments access to (more...)

First steps with Docker Checkpoint – to create and restore snapshots of running containers

Docker Containers can be stopped and started again. Changes made to the file system in a running container will survive this deliberate stop and start cycle. Data in memory and running processes obviously do not. A container that crashes cannot just be restarted and will have a file system in an undetermined state if it can be restarted. When you start a container after it was stopped, it will go through its full startup routine. (more...)

Ubuntu: unmet dependencies gparted (libparted-fs-resize0 (>= 3.1))

After a new ubuntu installation i got the following error:
root@pc:/etc/apt/sources.list.d# apt install   gparted
Paketlisten werden gelesen... Fertig
Abhängigkeitsbaum wird aufgebaut.   
Statusinformationen werden eingelesen.... Fertig
Einige Pakete konnten nicht installiert werden. Das kann bedeuten, dass
Sie eine unmögliche Situation angefordert haben oder, wenn Sie die
Unstable-Distribution verwenden, dass einige erforderliche Pakete noch
nicht erstellt wurden oder Incoming noch nicht verlassen haben.
Die folgenden Informationen helfen Ihnen vielleicht, die Situation zu lösen:
(more...)

A look into oracle redo, part 9: commit

The previous blogpost talked about a simple insert, this blogpost investigates what happens when the DML is committed. Of course this is done with regular commit settings, which means means they are not touched, which means commit_logging is set to immediate and commit_wait is set to wait as far as I know. The documentation says there is no default value, and the settings are empty in all parameter views. In my humble opinion, if you (more...)

A look into oracle redo, part 8: generate redo

This blogpost looks at the very start of oracle redo: the generation of it. In order to do that, I start off with a very simple table, and look at the redo generation part. I guess the regular readers of this blogpost series understand that redo generation is closely connected with making changes made to blocks. This post therefore is not only about redo generation, but also about how the technical implementation of block changes.

(more...)

A look into oracle redo, part 7: adaptive log file sync

This is the seventh part of a blog series about oracle redo.

Adaptive log file sync is a feature that probably came with Oracle version 11.2. Probably means I looked at the undocumented parameters of Oracle version 11.1 and do not see any of the ‘_adaptive_log_file_sync*’ parameters. It was actually turned off by default with versions 11.2.0.1 and 11.2.0.2, and was turned on by default since version (more...)

Stop password for user accounts expiring on Exadata

Depending on how the Oracle Exadata Machine was setup, the password for user accounts can expire thus requiring the password to be changed.

This has the knock on effect of the crontab not accessible and more importantly jobs do not run:

[oracle@v1ex1dbadm01 ~]$ crontab -l

Authentication token is no longer valid; new one required
You (oracle) are not allowed to access to (crontab) because of pam configuration.
[oracle@v1ex1dbadm01 ~]$

You can (more...)

Linux timing and scheduling granularity

During investigating how Oracle works with regards to waiting, I discovered an oddity. I was researching for my redo blog posts, and found that in a certain case, Oracle uses the ‘nanosleep’ system call. As the name of this system call suggests, this call allows you to let a process sleep with nanosecond precision.

The oddity that I found, was the following:

$ strace -Tp 42
...
nanosleep({0, 1000}, NULL)              = 0 <0.000253>
nanosleep({0, 1000},  (more...)

Method R Profiler on x86_64 Linux with HiDPI


For a new installed Linux Laptop I tried to install Method R Profiler (and Tools).
But it was not as smooth as expected.

mrprop_wrapper failed with

/opt/mrprof/mrprof_wrapper: line 45: /opt/mrprof-7.1.1.3-linux32/bin/mrprof.exe: No such file or directory
But the file is there, and it's executable.
So the Error is slightly misleading.
Also strace showed a similar error:
execve("/opt/mrprof-7.1.1.3-linux32/bin/mrprof.exe", ["/opt/mrprof-7.1.1.3-linux32/bin/"...], [/* 62 vars */]) = -1  (more...)

Where in the World Has Goth Geek Girl Been

I’m on track to fly home tomorrow, March 11th after nine days and three events.  I’m pretty exhausted and just ready to go home and catch up on some sleep…:)

I started out last weekend in Victoria BC and was thrilled to be on this emerald island of the Pacific Northwest.  British Columbia is gorgeous as it is, but Victoria is a special place that quickly became one of my favorite places in (more...)

Docker-CE on Ubuntu 17.10 (Artful Aardvark) (2)

Three months ago i installed docker on my ubuntu 17.10. At those days there was no straight forward howto on docher.com.

Now the installation is listed on docker.com:


The installation manual can be found here.

root@zerberus:~# apt-get install apt-transport-https ca-certificates curl   software-properties-common
root@zerberus:~# curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
  OK
root@zerberus:~# apt-key fingerprint 0EBFCD88  pub   rsa4096 2017-02-22 [SCEA]
      9DC8 5822 9FC7 DD38 854A  E2D8 8D81 (more...)

A look into Oracle redo, part 6: oracle post-wait commit and the on disk SCN

This is the sixth part in a blog series about Oracle database redo. The previous posts provided information about the log writer writing, this post is about the process that is waiting after issuing commit for the log writer to write it’s redo from the public redo strand. When the database is using post/wait for process commits, the committing process follows the following (simplified) procedure:

kcrfw_redo_gen_ext: 
 kcsgbsn8: kcsnew8: commit SCN is fetched from kcsgscn_
 kslgetl:  (more...)

Playing with Google Authenticator and Oracle Cloud – Securing SSH to Oracle account with two factor authentication

The Requirement Increase security when connecting via SSH to the Oracle OS account at Oracle Cloud by implementing two factor authentication (TFA or 2FA). The Environment Oracle Cloud Instance OS: Oracle Linux 6.9 The Implementation For this exercise we will

Can You DIG It?

As I dig deeper into Linux for the SQL Server DBAs and for Oracle HotSos, I’m digging into DIG.  Yeah, I went there with that first sentence….

What is DIG?

DIG stands for Domain Information Groper, (no, not that kind of groper…)  and it’s an important part of deeper Linux learning for all database technologists.  You can’t connect to data if you don’t know how to get from point A to point B (more...)

A look into Oracle redo, part 5: the log writer writing

| Feb 27, 2018

This the the fifth blog in a series of blogposts about Oracle database redo. The previous blog looked into the ‘null write’ (kcrfw_do_null_write actually) function inside kcrfw_redo_write_driver, which does housekeeping like updating SCNs and posting processes if needed, this blog looks into what happens when the log writer is actually posted by a process or if public redo strand buffers have been written into. In part 3 of this blog series (the log writer working (more…)

Ubuntu Kernel: Adding a new menuentry as default before menuentry ‘Ubuntu’ (grub)

After the problem with s2disk/hibernate on my Ubuntu 17.10 i wanted to change the grub boot menu:
I wanted to add my new default kernel at the beginning  - before the 'Ubuntu' menuentry.





Adding the menuentry inside /boot/grub/grub.cfg does not work, because after the first kernel update the command update-grub will overwrite all changes.

Easiest way:
Go to /etc/grub.d/ and move

mv 40_custom 09_custom
Inside 09_custom add your new menuentry (just copy (more...)

You may still need gcc when patching Oracle Database 12.2

I have previously written about changes in the Oracle 12.2 preinstall RPM and how gcc is no longer part of the dependencies list. As was pointed out to me, this shouldn’t be necessary anymore, according to the 12.2 Linux Database Installation Guide. Check the blue note for a statement indicating that gcc and gcc-c++ aren’t needed for Grid Infrastructure, nor for the RDBMS software.

I have applied patch 27100009 (January 2018 Release Update (more...)

Firefox tab crashes by loading maps.google.com on ubuntu 16.04

On a ubuntu 16.04 system firefox crashes by loading maps.google.com:

 The only way to fix this was going to "about:config":

On this page search for "webgl.disabled" and change the value from false
to true:

After that, maps.google.com loads without any problem...

Docker and Windows 10 1709 Patch, The End

So if you read my last post on my challenges with Docker containers running on Windows 10 after the 1709 patch, I thought I was close to solving it once I was granted the admin password to disable and uninstall Sophos Endpoint.

Once I uninstalled Sophos, I noted I ended up with a different line number error.  The question was, has the problem shifted from Sophos to a new issue or is it more (more...)