About Knowledge ReferencesChapter 5 Designing the Directory Topology 99• Dynamic management.You can add or remove a part of the directory from the system while the entiresystem remains available to client applications. The database link cantemporarily return referrals to the application until entries have beenredistributed across the directory. You can also implement this functionalitythrough the suffix itself, which can return a referral rather than forwarding aclient application on to the database.• Access control.The database link impersonates the client application, providing theappropriate authorization identity to the remote server. You can disable userimpersonation on the remote servers when access control evaluation is notrequired. For more information on configuring database links, refer to theNetscape Directory Server Administrator’s Guide.Deciding Between Referrals and ChainingBoth methods of linking your directory partitions have advantages anddisadvantages. The method, or combination of methods, you choose depends uponthe specific needs of your directory.The major difference between the two knowledge references is the location of theintelligence that knows how to locate the distributed information. In a chainedsystem, the intelligence is implemented in the servers. In a system that usesreferrals, the intelligence is implemented in the client application.While chaining reduces client complexity, it does so at the cost of increased servercomplexity. Chained servers must work with remote servers and send the resultsto directory clients.With referrals, the client must handle locating the referral and collating searchresults. However, referrals offer more flexibility for the writers of clientapplications and allow developers to provide better feedback to users about theprogress of a distributed directory operation.The following sections describe some of the more specific differences betweenreferrals and chaining in greater detail.
