samba - Aug 2007 - Samba Domain member server also with local user

Say I have a Samba PDC with LDAP SAM backend (say called PDC1).  Then I
have a domain member server ("security = domain", say called SERV1,
also
Samba); domain users can connect fine to access shares on SERV1.  Is it
also possible to create local users on SERV1 which can be stored in the
tdbsam backend and /etc/passwd, such that if login fails as a "domain
user",
then login can be attempted as a "local user"?  Then on successful
login
as a "local user", the connection proceeds based on the local
permissions
for that user.  Is this possible?

Perhaps it is needed to change SERV1 to "security = user", and then
set
"passdb backend = tdbsam:... ldapsam:...".  Would this do the job? 
Would
this cause any problems since now SERV1 is now a standalone server?

Thanks,
Leigh.