RE: [EXTERNAL] how to migrate an openldap server to a new linux server

I gave a try like this way: I installed an openldap 2.6 as target server, started it up with initial slapd.ldif. Then I tried to ldapadd entries that exported from source server, but failed on the first entry, error message:

[root@ldap-ol8 openldap]# ldapadd -H ldap:/// -D "cn=admin,dc=example,dc=com" -W -f /tmp/test.ldif adding new entry "dc=example,dc=com" ldap_add: Invalid syntax (21) additional info: objectClass: value #1 invalid per syntax

the ldif file like: dn: dc=example,dc=com dc: example objectClass: top objectClass: domain objectClass: nisDomainObject nisDomain: example.com

What's wrong with objectClass??