Is it possible to add a domain on an already existing root?

I got the following root for now:

dc=lab,dc=corp

and I want to create a second Top entry on my root which will be named like this:

dc=prod,dc=corp

Is that possible?

I've try the following syntaxe without succes.

Racine.ldif:

#Racine
dn: dc=prod, dc=corp
ObjectClass: Top
ObjectClass: dcObject
ObjectClass: organization
o: prod.corp
dc: prod

#OU Groups
dn: ou=groups, dc=prod, dc=geka
ObjectClass: organizationalUnit
ObjectClass: top
ou: groups

#OU Users
dn: ou=users, dc=prod, dc=geka
ObjectClass: organizationalUnit
ObjectClass: top
ou: users

And then I've done the usual LdapADD command, but with the following error returned:

ldap_add: Server is unwilling to perform (53)
Additional info: No global Superior Knowledge.

Well, my guest is that I didn't set correctly Slapd because my default root is lab.corp instead of being TLD .corp
Is that theory right?

Many thanks