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 LDAP parameter for redirecting clients to a master server for updates; it relates more to the Distinguished Name (DN) of an entry.

`updateserver` is not a standard LDAP parameter for specifying the master server for client redirection in this context.

The `updateref` parameter in an LDAP server's configuration specifies a URI or list of URIs of the master server. When a client tries to perform a write operation on a read-only slave, the slave returns a referral containing this `updateref` to direct the client to the master for write operations.

`updateuri` is not a standard LDAP parameter for client redirection; while URIs are used in `updateref`, `updateuri` itself is not the correct parameter name.