When a network node receives a search request, it checks its database for the resource. If it does not find the resource in its database, it sends the request to a central directory server if one exists in the network. If there is more than one central directory server in the network, the network node selects a central directory server based on one of the following possibilities:

• If the CDS selection function of the directory services management exit is active, the network node selects a central directory server from the list arranged by the exit. For information about how to use this function, see z/OS Communications Server: SNA Customization.
• If the CDSREFER start option value is 1 (the default), the network node sends the search request to the nearest (minimal weight route) central directory server in the network. For more information about the CDSREFER start option, see the z/OS Communications Server: SNA Resource Definition Reference. If the CDS selection function of the directory services management exit is active, then the CDSREFER start option value is used only for ordering the list of central directory servers passed to the exit.