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Daniel Westermann

Linux Magic System Request Key Hacks

By | Database Administration & Monitoring | No Comments

Recently at a customer we needed to power-cycle a database system because we wanted to be sure that a cluster resource fails over to a remaining node as expected. The issue was that we did not have access to the data center where the system is running nor did we have access to the console. What to do? Actually it is quite easy to force a system to reboot without syncing the disks or unmounting…

 
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Daniel Westermann

tmux – an alternative to screen

By | Database management | One Comment

You may already use screen for multiplexing a terminal. This is especially useful when you want to start long running processes on a server and do not want to loose the connection because of a ssh connection timeout, firewall settings or other reasons. With screen the session keeps running even if you got disconnected somehow and you may re-attach to the screen session at any point later. In this post I want to make you…

 
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Grégory Steulet

FIO (Flexible I/O) – a benchmark tool for any operating system

By | Operation systems | No Comments

I have just attended an interesting session held by Martin Nash (@mpnsh) at UKOUG 14 – Liverpool: “The least an Oracle DBA Should Know about Linux Administration” . During this session I had the opportunity to discover some interesting commands and tools such as FIO (Flexible I/O). FIO is a workload generator that can be used both for benchmark and stress/hardware verification. FIO has support for 19 different types of I/O engines (sync, mmap, libaio, posixaio,…

 
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Franck Pachot

Linux: how to monitor the nofile limit

By | Operation systems, Oracle | One Comment

By Franck Pachot . In a previous post I explained how to measure the number of processes that are generated when a fork() or clone() call checks the nproc limit. There is another limit in /etc/limits.conf – or in /etc/limits.d – that is displayed by ‘ulimit -n’. It’s the number of open files – ‘nofile’ – and here again we need to know what kind of files are counted. nofile ‘nofile’ is another limit that…

 
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Franck Pachot

Linux: how to monitor the nproc limit

By | Database Administration & Monitoring, Oracle | 16 Comments

By Franck Pachot . You probably know about ‘nproc’ limits in Linux which are set in /etc/limits.conf and checked with ‘ulimit -u’. But do you know how to handle the monitoring and be alerted when you’re close the fixed limit? Nproc and ps Nproc is defined at OS level to limit the number of processes per user. Oracle 11.2.0.4 documentation recommends the following: oracle soft nproc 2047 oracle hard nproc 16384 But that is often…

 
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Morgan Patou

How to install and manage a Kerberos Server

By | Application integration & Middleware | 5 Comments

For some time now, I have been working on how to set up a Single Sign-On (SSO) solution in my company. As a big fan of Open Source solutions, I have obviously proposed the implementation of a solution based on Kerberos. What I mean by that is a solution based on the true Kerberos, i. e. MIT Kerberos. Indeed, Kerberos was originally a research project at the Massachusetts Institute for Technology (MIT) in the early…

 
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Oracle Team

Troubleshooting: ORA-29283 when oracle is member of a group with read/write privileges

By | Database management | 6 Comments

Recently, I worked on an Oracle database migration for a customer and I faced a strange behavior when accessing a file stored on the file system of the Oracle database. The database has been migrated on a new server, and consolidated with existing databases. Several jobs are running into the database and need to access the file system to read or write some files. A particular file is received daily from a remote job over…

 
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Middleware Team

Boot sequence for all Linux-based operating systems

By | Operation systems | No Comments

In this bog posting, I will present a boot sequence that works for all Linux-based operating systems – from switching on the power to the login screen.   7 steps There are 7 steps for Linux startup: Power on Obviously, first of all, you have to switch on your computer, then: Each sub process will execute the following one It is the same process for all Linux distributions Close to BSD and Unix style from…

 
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Overview of Oracle Linux releases and kernels

By | Operation systems | 2 Comments

As everybody knows, Linux regroups several operating system families. The most popular Linux OS are Debian, Red Hat, or Suse. But each family has many derived Linux distributions. In November 2006, Oracle released the first version of its operating system, totally based on Red Hat Enterprise Linux: Enterprise Linux. Up to release 5, the system came with two kernels: A customized kernel with bug fixes, based on Red Hat kernel, installed and started by default…

 
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Yann Neuhaus

Oracle Automatic Memory Management: real memory usage!

By | Database management | One Comment

When using Automatic Memory Management for Oracle, it is sometimes difficult to monitor the memory usage and in particular to find the right tools to get the right information about currently allocated structures. The instance which will be analyzed has been configured with AMM (Automatic Memory Management) on Oracle Enterprise Linux 6.1. The current memory_target is set to 1 GB: SQL> show parameter memory_target NAME                                 TYPE        VALUE ———————————— ———– ———— memory_target                        big integer 1G  …

 
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