Queuing and clustering

Cloning application servers can be a valuable asset in configuring highly-scalable production environments, especially when the application is experiencing bottlenecks that are preventing full CPU utilization of symmetric multiprocessing (SMP) servers. When adjusting the WAS system queues in clustered configurations, remember that when a server is added to a cluster, the server downstream receives twice the load.

Two servlet engines are located between a Web server and a data source. It is assumed that the Web server, servlet engines and data source, but not the database, are all running on a single SMP server. Given these constraints, the following queue considerations must be made:

• Double the Web server queue settings to ensure ample work is distributed to each Web container.

• Reduce the Web container thread pools to avoid saturating a system resource like CPU or another resource that the servlets are using.

• Reduce the data source to avoid saturating the database server.

• Reduce Java heap parameters for each instance of the application server. For versions of the Java virtual machine (JVM) shipped with WebSphere Application Server, it is crucial that the heap from all JVMs remain in physical memory. For example, if a cluster of four JVMs is running on a system, enough physical memory must be available for all four heaps.

 

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