Karan Rajpoot Oracle DBA Blog's

         TNS-12547: TNS:lost contact TNS-12560: TNS:protocol adapter error TNS-00517: Lost contact Error: - "TNS-12547: TNS: lost contact TNS-12560: TNS: protocol adapter error TNS-00517: Lost contact" Cause: - This error occurs when loopback entries have been missed in the /etc/hosts file. Solution: - To resolve this error you need to put the loopback entries in the /etc/hosts file. Example: -  [oracle@prod bin]$ lsnrctl start LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 14-APR-2019 22:08:16 Copyright (c) 1991, 2013, Oracle.  All rights reserved. Starting /u02/app/oracle/product/11.2.0/db_1/bin/tnslsnr: please wait... TNSLSNR for Linux: Version 11.2.0.4.0 - Production System parameter file is /u02/app/oracle/product/11.2.0/db_1/network/admin/listener.ora Log messages written to /u02/app/oracle/diag/tnslsnr/prod/listener/alert/log.xml Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=prod.radical.com)(PORT=1521))) C

                                                        Destination Host Unreachable in Linux Error: -  icmp_seq=2 Destination Host Unreachable Cause: - When you are trying to ping Linux machine from one node to another node then you may face issue "destination host unreachable", the reason behind this issue is the selection of network while creation of Linux machine. Solution: - To resolve this issue you need to select the proper network selection. Example: - In this case, there are two machine prod and dr, When I was tried to ping dr machine from prod then I faced below issue. I checked so many things like firewall, etc/hosts file entries and so on, but didn't get resolution then, at last, I checked my network configuration and found it was set as NAT. I have changed the Network from NAT to the host-only adapter and then tried again finally, that issue has been resolved. Before changing the network from NAT to Host-only adapter. [root@prod Desk

                          Below are the steps to Install Linux on Oracle Virtual Box Step 1) First you need to download the Oracle Virtual Box from the link . Step 2) Select New Option to choose the name, type, and version of the Operating system. Step 3) Select the Memory as per your requirement. Step 4) Choose the Hard disk options as Create a Virtual Hard disk Now. Step 5) Choose the Hard disk file type as VDI (Virtual Disk Image). Step 6) Select Storage on a physical hard disk as Dynamically allocated or  Fixed size as per your requirement. Step 7) Select the File Location and Size as per your requirement. Step 8) Now go to the Storage tab and select the ISO image file which needs to be installed. Step 9) Now Click on the Start tab  to initialize the installation. Step 10) Now click on the Install or Upgrade an existing system to proceed further in the installation. Step 11) Click on the Skip tab to skip the med