Create Oracle Database Link

DROP DATABASE LINK link001;
-- create in same db.
CREATE DATABASE LINK link001 CONNECT TO myuser IDENTIFIED BY mypassword USING 'SID1'

--create in different db.
CREATE DATABASE LINK  link001
CONNECT TO myuser IDENTIFIED BY mypassword
USING '(DESCRIPTION =
    (ADDRESS_LIST =
        (ADDRESS = (PROTOCOL = TCP)(HOST = HOSTNAME_OR_IP)(PORT = 1521))
    )
    (CONNECT_DATA =
        (SERVICE_NAME = SID1)
    )
)';