ORA-02082

ORA-02082: a loopback database link must have a connection qualifier

The issue occurs when there is a db link which is a loop back database link i.e. points to itself
For Example:
HRMS@> DROP DATABASE LINK SHAAN.WORLD;
DROP DATABASE LINK SHAAN.WORLD
*
ERROR at line 1:
ORA-02082: a loopback database link must have a connection qualifier
 

Solution:

Query the Global name and note down that name.

HRMS> select * from global_name;
GLOBAL_NAME
-----------------------
SHAAN.WORLD
1 row selected.

Now rename this global with some other name to fix the actual issue.
HRMS@> Alter database rename global_name to SHAAN1.XXXX;
Database altered.

Now you will able to delete the database link as the global name is seperated from the DBlink
HRMS@> DROP DATABASE LINK SHAAN.WORLD;
Database link dropped.

After dropping the dblink rename back to your global name.
HRMS@> Alter database rename global_name to SHAAN.WORLD;
Database altered