The connection desription for the orcl2 database has to be in tnsnames.ora on the orcl server, not on the client.

As an option, you can put the whole connection description into the create database link statement:

SQL> create database link orcl2_lnk connect to scott identified by
tiger using '(DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(PORT = orcl2_port)(HOST = orcl2_host))) (CONNECT_DATA = (SERVICE_NAME = orcl2_service_name)))';