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   Introducing the BEA Tuxedo System

Load balancing is a technique used by the BEA Tuxedo system for distributing service requests evenly among servers that offer the same service. This avoids overburdening some servers while leaving others idle or infrequently used. Before sending a request to a service routine, the system identifies all servers capable of handling the request and selects the one most appropriate for maintaining a balanced load across all the servers in the configuration.

Load refers to a number assigned to a service request based on the amount of time required to execute that service. Loads are assigned to services so that the BEA Tuxedo system can understand the relationship between requests. To keep track of the amount of work, or total load, being performed by each server in a configuration, the administrator assigns a load factor to every service and service request. A load factor is a number indicating the amount of time needed to execute a service or a request. On the basis of these numbers, statistics are generated for each server and maintained on the bulletin board on each machine. Each bulletin board keeps track of the cumulative load associated with each server, so that when all servers are busy, the BEA Tuxedo system can select the one with the lightest load.

You can control whether a load-balancing algorithm is used on the system as a whole. Such as algorithm should be used only when necessary, that is, only when a service is offered by servers that use more than one queue. Services offered by only one server, or by multiple servers in an MSSQ (multiple server single queue) do not need load balancing. The LDBAL parameter for these services should be set to N. In other cases, you may want to set LDBAL to Y.

To determine how to assign load factors (in the SERVICES section of UBBCONFIG), run an application for a long period of time and note the average time it takes to perform each service. Assign a LOAD value of 50 (LOAD=50) to any service that takes roughly the average amount of time. Any service taking longer than average should have a LOAD>50; any service taking less than the average should have a LOAD<50.