Caution should be exercised though, if, for example, the amount of data being replicated in a shadow agreement is great then the shadow operation itself can cause service degradation!
• Country Level
Replication of the country level is necessary to reduce the need for access to first level servers, which tend to respond slowly due to excessive usage and also to limit the number of simultaneous connections supported. In this case the amount of data copied is minimal and the performance gain is appreciable, and so should be configured into EuroView backbone and user DSAs.
• Organizational Level
In some instances it may be necessary to replicate the entirety of an organization's directory data between EuroView DSAs. Replication may well be critical in the Spanish case where a relay DSA will be employed to provide connectivity. As this is a single point of access between directory communities (the Spanish X.25 users and the rest of the EuroView service) any server downtime or network failure would result in loss of service. Replicating Spanish user data to each of the central services will add a large degree of fault tolerance to the system and improve performance greatly. This may present a resource problem depending on how much data is stored by the Spanish contingent.