Which ONE of the following parameters is used in the database on a slave server to direct clients that want to make changes to the LDAP database to the master server?

`updatedn` is not a standard OpenLDAP directive for referring clients to a master server for updates.

`updateserver` is not a standard OpenLDAP directive for referring clients to a master server for updates.

In an OpenLDAP replication setup, the `updateref` directive (configured in `slapd.conf` for the slave database) is used to specify a URL pointing to the master server. When a client attempts a write operation (e.g., add, modify, delete) on a read-only slave, the slave returns this `updateref` URL, informing the client where to redirect its write request to the authoritative master server.

While `updateuri` might seem plausible, the standard and correct directive for this purpose in OpenLDAP's `slapd.conf` is `updateref`. `uri` is often used in other contexts for specifying a server address, but `updateref` is specific to this referral mechanism.