Validating the database connection

From the application server, open a command prompt and issue the command
sqlplus system/system_password@alias_in_tnsnames.ora

If the test is successful, an SQL prompt appears, and a connection is established to the database server as the user system.

If the test is unsuccessful, you receive an ORA-error. For help with troubleshooting errors, Consult your DBA.

Note: Problems with connections can sometimes be attributed to the database server containing a single Ethernet card with two nodes. Disabling one of the ports from the card usually solves the problem. For help with resolving errors, consult your system administrator.