In a distributed environment, Cognos 8 balances request load automatically. By default, as servers are added to the system, each server dispatcher processes the same number of requests. If there is more than one instance of a given service, the dispatcher distributes requests to all the enabled instances of the service that are registered in Content Manager.
Load Balancing Dispatchers
Without a software or 
hardware load balancing mechanism, each Cognos 8 gateway is aware of
only one dispatcher, and distributes all requests to that dispatcher. The dispatcher then distributes the requests among Cognos 8 servers. Because every request initially goes through the same dispatcher on one server, the load on that server is increased. An extra step is needed to automatically balance the load, as shown in the following diagram.
Load Balancing Without an External Mechanism
Since gateway servers often have less load than Cognos 8 servers, you may achieve better performance by configuring dispatchers together with the gateways, as shown in the following diagram.
This ensures that the processing capacity of the Cognos 8 servers is directed toward serving report requests rather than load balancing requests.
You can also achieve load balancing by having gateways direct all traffic to a Cognos 8 server
computer that is dedicated to dispatching, as shown in the following diagram.
This configuration also removes dispatching load from the Cognos 8 servers. However, it does
require separate dispatching computers.
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