UNIX connectivity for Oracle - DBA TNS service Oracle Tips by Burleson Consulting

UNIX connectivity for Oracle

When the Oracle DBA creates their tnsnames.ora file to define remote databases they often specify the host name of the foreign server that contains the remote Oracle database. For example, a entry in the tnsnames.ora file for a remote database might look like this:

berlin =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS =
(COMMUNITY = TCP)
(PROTOCOL = TCP)
(HOST = hun)
(PORT = 1521)
)
)
(CONNECT_DATA = (SID = kraut))
)

Here we see a TNS service name of berlin, which defines a connection to a remote server named hun that contains an Oracle database named kraut. When a remote connection request is made from the UNIX server, the /etc/host file is accessed to get the IP address for the hum server. From the listing below, we see that the hun server is located at 192.133.13.12. In sum, the /etc/host file is used to isolate the IP address from the tnsnames.ora file. If the IP address should ever change, the UNIX systems administrator only needs to change the IP address in one place.

root> cat /etc/hosts

192.133.13.22 hun hun.com
192.144.13.22 dopey dopey.com

Next, let’s start looking at UNIX commands and begin by exploring their similarity to MS-DOS commands for the PC.

The above is an excerpt from the "Oracle9i UNIX Administration Handbook" by Oracle press, authored by Donald K. Burleson.