How do I generate a tnsnames.ora file to connect to an Oracle Database?

You can easily create a tnsnames.ora [text] file. It should be in $ORACLE_HOME/network/admin/ and should look something like this:

 ORATST=
 (description=
   (address_list=
     (address = (protocol = TCP)(host = fu.bar)(port = 1521))
   )
 (connect_data =
   (service_name=oratst)
 )
)

The default directory for a tnsnames.ora file is

/u01/app/oracle/product/<version>/<dbname>/network/admin/tnsnames.ora

Contents:

<alias> = (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = <ip>)(PORT = <port>))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = <dbname>)
    )
  )

• alias: you can choose this and use it as connection string later on.
• port: the default is 1521

More info here: http://docs.oracle.com/cd/B28359_01/network.111/b28317/tnsnames.htm

If your OS is Windows 10, you can find tnsnames.ora file in the following unc path:

C:\app\myAccount\product\11.2.0\dbhome_1\NETWORK\ADMIN

Where myAccount is your Windows account name.