ORA-12514: TNS: Issue

ORA-12514: TNS: Listener does not currently know of service requested in connect descriptor

Solution:
1) Check the tnsnames.ora file for the service name specified correcttly and it should exist as shown below for an example.

ORCL =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.6.134)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl)
    )
  )

2) Check the listener service is running on the server where oracle database is installed.

>LSNRCTL STATUS

3) You can try to stop and start the listener service

>LSNRCTL STOP
>LSNRCTL START