The following example describes Oracle database operations at the most basic level. It illustrates an Oracle database configuration in which the user and associated server process are on separate computers, connected through a network. 1. An instance has started on a node where Oracle Database is installed, often called the host or database server. 2. A user starts an application spawning a user process. The application attempts to establish a connection to the server. (The connection … [Read more...] about How an SQL query is executed in Oracle Database
How to Disable/Enable Numa for Virtual Machine (XEN based)
How to check if NUMA is enabled To determine if the server is a NUMA-based system with NUMA enabled, run the following command as root on the database server: # numactl -H | grep available available: 8 nodes (0-7) - or - # numactl -H | grep available available: 2 nodes (0-1) If the number of available nodes is "2 nodes (0-1)" or "8 nodes (0-7)" then NUMA is enabled. If the number of available nodes is "1 nodes (0)" then NUMA is not enabled. How to disable Numa on Virtual … [Read more...] about How to Disable/Enable Numa for Virtual Machine (XEN based)
LVM and multipathing – sample LVM filter strings
The post is intended for Linux System Administrators seeking to initially configure or further optimise existing LVM configured systems. It discusses: the need for specific LVM filter string configuration for the particular storage type in use. provide sample LVM filter strings for a variety of common storage devices LVM Configuration - filter parameter The primary LVM configuration file is /etc/lvm/lvm.conf. The file consists of a number of sections each containing various … [Read more...] about LVM and multipathing – sample LVM filter strings
lvdisplay error: “Failed to create directory /var/lock/lvm. File-based locking initilisation failed.”
The Problem lvdisplay command prints the below error on a CentOS/RHEL 6 system: # lvdisplay Failed to create directory /var/lock/lvm File-based locking initilisation failed. The Solution The above error is due to the /var file system is mounted as read only. To resolve the issue, follow the steps outlined below: 1. Edit and modify /etc/lvm/lvm.conf as below: locking_dir = "/var/lock/lvm" to locking_dir = "/tmp/lock/lvm" 2. Run the lvm commands by defining temporary locking … [Read more...] about lvdisplay error: “Failed to create directory /var/lock/lvm. File-based locking initilisation failed.”
List of ports required by Oracle VM
This post describes the list of ports used by Oracle VM Manager and Oracle VM Server. Configuring firewalls to allow for proper connectivity to and between required ports will help to ensure successful Oracle VM operation. The following table describes the list of ports used by Oracle VM Manager and Oracle VM Server. Some of these can be configured/changed manually, so these are default values. Oracle VM Server PortProtocolService 25tcpsendmail 631tcp/udpinternal use (CUPS) … [Read more...] about List of ports required by Oracle VM
The System Continuously Displayed the Error Message from the “avahi-demon” in /var/log/messages
The Problem The server continuously displaying below messages in /var/log/messages or dmesg log file: avahi-daemon[23373]: server.c: Packet too short or invalid while reading response record. (Maybe an UTF8 problem?) The Solution This is avahi-daemon issue related to network environment. The avahi-daemon is application for zeroconf implementation. The avahi-daemon working related of to DNS(mDSN). The avahi-daemon approaching and searching to each other user or devices for local network … [Read more...] about The System Continuously Displayed the Error Message from the “avahi-demon” in /var/log/messages
How the BASH Shell load its configuration files in Linux
BASH Shell will attempt to load several configuration files during the initialization. There are 2 sets of configuration files, depending it's a login-shell, or non-login shell. When you login a server on a bare metal monitor, or via SSH, or with # su - [username], you get a login shell. When you start a shell in a terminal in an existing session (gnome-terminal, a shell inside another, or with # su [username]...), you get a non-login shell. A shell script is also executed under a non-login … [Read more...] about How the BASH Shell load its configuration files in Linux
RMAN Pluggable Database Backup and Recovery in a Multitenant Environment
What is a Container Database? A 12c database is either a non-Container Database or a Container Database - from here on referred to as non-CDB or CDB respectively. All databases created prior to 12c are non-CDBs. A CDB is an Oracle database that includes zero, one, or many customer-created Containers or Pluggable Databases referred to as PDB. The CDB has: one ROOT container (CDB$ROOT) containing SYSTEM, SYSAUX, UNDO, and TEMP tablespaces, Controlfiles and Redologs one SEED container … [Read more...] about RMAN Pluggable Database Backup and Recovery in a Multitenant Environment
How to Mount NFS File Systems Using ‘autofs’ in CentOS/RHEL
This post explains how to configure 'autofs' in order to mount NFS file systems with 'autofs' service. 1. Stop 'autofs' service, check if the service is running then proceed to stop it. # service autofs status automount (pid 25285) is running... # service autofs stop Stopping automount: [ OK ] # service autofs status automount is stopped 2. Edit the /etc/auto.master file to set the file map: The file /etc/auto.master is the main configuration file for 'autofs' service, this file … [Read more...] about How to Mount NFS File Systems Using ‘autofs’ in CentOS/RHEL
How To Configure SNMP Daemons: snmpd and snmptrapd on CentOS/RHEL 5,6 and 7
For CentOS/RHEL 5 and 6 On CentOS/RHEL 5 there is no configuration file for snmptrapd.conf. As per manual pages "The Net-SNMP notification receiver (trap daemon) uses one or more configuration files to control its operation and how incoming traps(and INFORM requests) should be processed. This file (snmptrapd.conf)can be located in one of several locations, as described in the snmp_config(5) manual page." The configuration file /etc/snmp/snmptrapd.conf can be manually created if it doesn't … [Read more...] about How To Configure SNMP Daemons: snmpd and snmptrapd on CentOS/RHEL 5,6 and 7