HP-UX Directory Server Administrator Guide HP-UX Directory Server Version 8.1 (5900-3332, November 2013)

The nsslapd-state attribute can also be set to referral on update. This means that
the database is used for all operations except update requests. When a client application
makes an update request to a suffix set to referral on update, the client receives a
referral.
For more information about the suffix configuration attributes, see Table 2 (page 36).
Using Referrals 95