Create DB link

Run this script on source DB

CREATE DATABASE LINK "ORASUPD_WORLD.REGRESS.RDBMS.DEV.US.ORACLE.COM"
CONNECT TO OIM_USER
IDENTIFIED BY pwd
USING 'ORASUPD.WORLD';

create database link "my1"
connect to oim_user
identified by "manager1"
using '(DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = hostname)(PORT = 1521)))(CONNECT_DATA =(SERVICE_NAME= ORASUPD.WORLD) ) )'

insert into rep@ORASUPD_WORLD
select * from rep
where rep_key >18
and rep_key not in (select rep_key from rep@ORASUPD_WORLD)