[Samba] LDAP passdb backends. What's the difference?

[Jim C]

I've not be able to find in the docs where it describes the differences 
between ldapsam ldapsam_nua etc. etc.   I don't have access to the man 
pages and I've checked the online documentation also.  Something has 
been going wrong in my config and I think a better understanding of 
these may help.

I do know that ldapsam_compat is supposed to be backward compatible with 
the old LDAP schema thus I assume that the others are not.

Jim C.