dblink issue.

Hello DBAs..

I createde  a db link in dev env to copy some tables from prod whenever need. while i am teting i am getting below error. please help me to fix this..

create public database link ptprd.world using 'ptp.world';

create database link ptpda.world connect to nbkeqeo identified by xxxx using 'PTP.WORLD';

OWNER           DB_LINK            USERNAME             HOST
--------------- ------------------ -------------------- --------------------
NBKEQEO         PTPDA.WORLD        NBKEQEO              PTP.WORLD
PUBLIC          PTPRD.WORLD                             ptp.world

SQL> select * from dual@PTPDA.WORLD;
select * from dual@PTPDA.WORLD
                   *
ERROR at line 1:
ORA-02019: connection description for remote database not found

SQL> select * from