DB LINK Creation 

CREATE DATABASE LINK "DB_LINKNAME"
 CONNECT TO user_name
 IDENTIFIED BY password
 USING '(DESCRIPTION=
    (ADDRESS=
      (PROTOCOL=TCP)
      (HOST=HOST_NAME)
      (PORT=1523)
    )
    (CONNECT_DATA=
      (INSTANCE_NAME=INS_NAME)
      (SERVICE_NAME=SERVICE_NAME)
    )
  )';