ORA 12514 error:TNS listener error :


Probable reasons and solutions :

One of the reasons you get that kind of error is because database instance started before listener did. Listener must always be started first.

    - Check if a database instance up and running.

    - Check the output of the lsnrctl service command and see what services are registered.

    - Check if you has SERVICE_NAME correctly specified when connecting to the instance.

    - If it happens that database instance stared before listener did sometimes you just need to wait a little or you can execute alter system register in order to register the instance.

    - Add the SID entry in TNSNAMES.ORA :

SID_NAME =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST =hostname)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = SID_NAME)
    )
  )

Cheers!