How to Add a TNS Entry on a Local Host

A guide to configuring your Windows `hosts` file to connect to Oracle Apps R12.

Understanding the `hosts` File

Before you can connect to an Oracle database using a hostname (like `ebs.example.com`) in your `tnsnames.ora` file, your computer needs to know which IP address that hostname points to. The Windows `hosts` file is a simple text file that acts as a local DNS resolver, allowing you to manually map IP addresses to hostnames. This guide shows you how to edit it.

Step-by-Step Guide

Step 1: Open Notepad as Administrator

Click on the Start menu, search for 'Notepad', right-click on it, and select 'Run as administrator'. This is crucial because the hosts file is a protected system file.

Step 2: Open the 'hosts' file

In Notepad, go to File > Open. Navigate to the directory C:\Windows\System32\drivers\etc. You may need to change the file type from 'Text Documents (*.txt)' to 'All Files' to see the 'hosts' file. Select it and click Open.

Step 3: Add the Host Entry

Go to the end of the file and add a new line for your Oracle server. The format is IP Address, followed by a space or tab, and then the hostname. For example: 192.168.1.5 ebs.example.com

Step 4: Save the File

After adding the entry, go to File > Save to save your changes. You can now use the hostname 'ebs.example.com' in your tnsnames.ora file or other connection tools, and your computer will know it points to 192.168.1.5.

Important Note

The default setup for an Oracle Vision Instance might be something like:

Host IP Address: `192.168.1.5` (This will vary based on your network)
Port Number: `1521`
SID (Service Identifier): `EBSDB`

The `hosts` file only handles the IP to hostname mapping. The port and SID will be used in your `tnsnames.ora` configuration.