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Archives for December 2018

How to configure xhost to be persistent across reboots in Linux

by admin

Introduction The xhost command is the Linux X-Windows server access control program. Depending on the arguments used, xhost grants or denies user/host access (connections) to the local X-server, thereby allowing or denying users/hosts the ability to display X-Windows-based applications e.g. xclock, graphical installers etc. The purpose of this post is to describe how to configure […]

Filed Under: Linux

Oracle 12.2 : RMAN Cross-Platform Transport of PDB into Destination CDB

by admin

Introduction and Pre-requisites Using RMAN, Pluggable database (PDBs) can be transported and plugged into a destination multitenant container database (CDB) which is on a different platform than the source CDB. In addition to the backup of the PDB, RMAN also copies the metadata required to plug the PDB into the destination CDB. The source CDB […]

Filed Under: oracle, oracle 12c

How to Change default Oracle database listener port (1521)

by admin

By default, after installing Oracle Database Server, the Listener service will wait for and accept connections on TCP port 1521. However, it is possible to reconfigure the listener to use a different port. The procedure comprises two steps: reconfiguring the listener. reconfiguring the database instance(s) to register to the listener on the new, non-default port. […]

Filed Under: oracle

IPv4 Subnet Basics and Oracle Clusterware

by admin

What’s IPv4 Subnet The IP subnet is a logical separation of IP addresses bounded by the subnet mask. The first address is used as the Subnet Identification (subnet ID or subnet number or route definition) while the last is the broadcast address. For example, subnet ID 10.1.0.0 and netmask 255.255.255.128 produces an IP range of […]

Filed Under: oracle, RAC

Example of PDB Level Duplication in Oracle Database 18c

by admin

In the database versions before 18c, PDB could not be duplicated. Users could only duplicate CDBs. But starting with Oracle database 18c, users can now duplicate one PDB into another CDB. This post gives an example of how to do it. Example Environment Here is an example of how to duplicate PDB from one CDB […]

Filed Under: 18c, oracle

Oracle Database 18c new feature – Scalable Sequences

by admin

Starting 18.1 database, “Scalable Sequences” have been introduced. The ability to create Scalable Sequences has been added to improve the performance of data loading into tables having sequence values as keys. This feature provides the option to add instance and session offsets to significantly reduce the possibility of sequence and index block contention when loading […]

Filed Under: 18c, oracle

How To Cancel A SQL Query In Oracle Database 18c

by admin

The idea of this post is to explain the steps to cancel a query in Oracle Database 18c. In this version, you have the option to cancel just the query instead of terminating the session. The following clauses are required in an “ALTER SYSTEM CANCEL” SQL statement: SID – Session ID SERIAL – Session serial […]

Filed Under: 18c, oracle

How to set children-max for udev Service in CentOS/RHEL 7

by admin

This post will outline steps to set children-max in CentOS/RHEL 7 temporarily and permanently. Temporary set children-max for udev Service To change temporarily, without rebooting: # systemctl status systemd-udevd.service … Status: “Processing with ## children at max”

Filed Under: CentOS/RHEL 7, Linux

How to persistently set nr_requests using UDEV rules

by admin

The nr_requests is a parameter for block device, it controls maximum requests may be allocated in the block layer for read or write requests, the default value is 128. Occasionally, it may be suggested to adjust the value, generally speaking: Increasing the value will improve the I/O throughput, but will also increase the memory usage. […]

Filed Under: CentOS/RHEL 5, CentOS/RHEL 6, CentOS/RHEL 7, Linux

Starting udev: udevd inotify_init failed: too many open files

by admin

The Problem After a server has been restarted after patching – The error below can possibly be witnessed during boot and the same error is visible in /var/log/boot.log: Starting udev: udevd inotify_init failed: too many open files Due to udev fails to start, network and bonding interfaces are missing (including modules/drivers). The Solution There was […]

Filed Under: CentOS/RHEL 6, CentOS/RHEL 7, Linux

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