How GDS Works
When an application program makes a Global Directory Service call using the XDS API, the call is handed to the DUA library. The DUA first looks in the DUA Cache (if specified) to see if the requested information is already available on the local node. If it is not, the DUA queries a Directory Service Agent. The DSA may have the requested information, and if it does it returns the results to the DUA. If it does not, the query can proceed in one of two ways. Either the DSA can query a different DSA on behalf of the DUA, or the DSA can return information such that the DUA can query a second DSA itself. The first method is called chaining and the second method is called referral. In either case, different DSAs are queried until the information is found. It is cached (if specified) in the DUA cache and the results are returned to the GDS application program.