ORA-12504: TNS:listener was not given the SERVICE_NAME in CONNECT_DATA

Error
Error occured while tried to access the SQL query of DBLINK.
ORA-12504: TNS:listener was not given the SERVICE_NAME in CONNECT_DATA

SELECT sales_item
FROM sales_north@SALE_DBLINK
WHERE sales_id = 785;

FROM sales_north@SALE_DBLINK
*
ERROR at line 2:
ORA-12504: TNS:listener was NOT given the SERVICE_NAME IN CONNECT_DATA


Cause
service entry not exists in the TNSNAMES.ora file or may it has wrong entry.

Solution
1. Check the TNSNAMES.ORA file exists.

2. Check the tns entry present in the TNSNAMES.ORA file.

SALESDB =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.2)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = SALESDB)
)
)


3. Check DB link is present in the Database.

select * from USER_DB_LINKS


Following are example of creating SALESDB link use in above example:

CREATE DATABASE LINK SALE_DBLINK
CONNECT TO SALEUSER IDENTIFIED BY salespassword
USING 'SALESDB';