Some values that may affect performance are:
response-timeout-in-seconds -The time for which the load balancer plug-in will wait for a response before it declares an instance dead and fails over to the next instance in the cluster. Make this value large enough to accommodate the maximum latency for a request from the server instance under the worst (high load) conditions.
health checker: interval-in-seconds - Determines how frequently the load balancer pings the instance to see if it is healthy. Default value is 30 seconds. If the response-timeout-in-seconds is optimally tuned, and the server doesn’t have too much traffic, then the default value works well.
health checker: timeout-in-seconds - How long the load balancer waits after “pinging” an instance. The default value is 100 seconds.
The combination of the health checker’s interval-in-seconds and timeout-in-seconds values determine how much additional traffic goes from the load balancer plug-in to the server instances.
For more information on configuring the load balancer plug-in, see Configuring the Load Balancer in Sun Java System Application Server Enterprise Edition 8.2 High Availability Administration Guide.