Check Connection String:

# sqlplus sys/password@'(DESCRIPTION=(ADDRESS = (PROTOCOL = TCP)(HOST = host1.test.com)(PORT = 1521))(CONNECT_DATA=(SERVER = DEDICATED)(SERVICE_NAME=host1)))' as sysdba

 Enter password:

ERROR:

ORA-12541: TNS:no listener

 If you get error like above. Check listener is running and the service is added in the listener.

# lsnrctl status (If your listener is stop then start your listener using “lsnrctl start”)

ORA-12514: TNS:listener does not currently know of service requested in connect Descriptor

If you get error like above check service in listener.

# lsnrctl services (If service is not in the list add the service)

Check connection string after fixing:

# sqlplus sys/password@'(DESCRIPTION=(ADDRESS = (PROTOCOL = TCP)(HOST = host1.test.com)(PORT = 1521))(CONNECT_DATA=(SERVER = DEDICATED)(SERVICE_NAME=host1)))' as sysdba

 SQL*Plus: Release 11.2.0.3.0 Production on Fri Feb 28 16:07:16 2014

 Copyright (c) 1982, 2011, Oracle.  All rights reserved.

 Enter password:

 Connected to:

Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - 64bit Production

With the Partitioning option

SQL> select host_name from v$instance;

 HOST_NAME

--------------------------------------------------------------------------------

host1.test.com