How does slapd get "secret" for a DN?

[ctosgh]

Greetings,
 
As section 15.2.3 in http://www.openldap.org/doc/admin24/sasl.html said
"The server's copy of the shared-secret may be stored in Cyrus SASL's own 
sasldb database, in an external system accessed via saslauthd, or in LDAP 
database itself"
 
How does slapd know where the secret is stored? Does slapd try each place in a 
predefined sequence?
 
Thanks,
Jacky