How do I use the Instant Client client to connect to an Oracle database?

To connect to an Oracle database using the Instant Client client, you need to follow the steps below:

1. Download and install the Oracle Instant Client: First, you need to download and install the Oracle Instant Client suitable for your operating system from the official Oracle website. The installation process may require you to set up environment variables.
2. Set up Oracle Instant Client by configuring the environment variables so that the system can find the client program. You can add the path of Instant Client to the system’s PATH environment variable.
3. Edit the TNSNAMES.ORA file: Locate the TNSNAMES.ORA file in the network folder of your Instant Client and configure the connection information. Add the hostname, port number, service name, and any other necessary details for the Oracle database you want to connect to.
4. Test connection: Use sqlplus or other tools that support Oracle connections in the command line, enter the connection string, and test the connection.

For example, if you have a connection information in your TNSNAMES.ORA file like the following:

ORCL =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl)
    )
  )

You can use the following commands to test the connection:

sqlplus username/password@ORCL

The username and password are the credentials used to login to the database, and ORCL is the alias for the connection information configured in TNSNAMES.ORA.

By following the above steps, you can now connect to an Oracle database using Oracle Instant Client.