Samba 3 stores information about its domain settings inside LDAP. This includes the domain name, its SID and some policies. You can manage all these attributes with LAM.
Please activate the account type "Samba domains" in your LAM server profile. Please notice that Samba by default uses the LDAP root for domain objects (e.g. dc=example,dc=com).
This will add a new tab to LAM where you can manage domain information.
The domain name, SID and RID base can only be specified for new domains and are not changeable via LAM at a later time. You may setup several password policies for your Samba domains and also some RID options that influence the creation of SIDs for users/groups/hosts.