WebSphere Virtual Enterprise, Version 6.1.1
             Operating Systems: AIX, HP-UX, Linux, Solaris, Windows, z/OS


Overriding work factor estimates

Use this task to override the values that are computed by the work profiler.

Before you begin

If you have already specified a speed factor override, you do not need to configure a work factor override. See Configuring speed factors in multiple tier configurations for more information about speed factors.

About this task

The work profiler computes a work factor for each transaction class module (TCM). Specifying the override depends on the version of the product that you are using. In WebSphere Extended Deployment Version 5.1, explicit transaction classes were specified. In WebSphere Extended Deployment Version 6.0 and later, you can use work classes to classify work into transaction classes.

When using explicit transaction classes like in WebSphere Extended Deployment Version 5.1, each TCM is stored in the file that defines the service class to which it belongs. A service class is defined by a profile/config/cells/cell name/serviceclasses/service class name/serviceclass.xml file. In this file, each <TransactionClassModules> element defines a single TCM, and you can attach a workFactor attribute to override the work profiler calculations for that TCM.

When you are using work classes, an XML element does not exist for each TCM. In this case, the work factor overrides related to a given deployment target (cluster, or unclustered server) can be specified in a custom property that is attached to that deployment target.

Use the workFactorOverrideSpec custom property. The value for this custom property is a string that contains a set of matching rules, or cases, that define the work factor override, either a value or none, for every TCM of that deployment target. The syntax of that string is the same as the syntax of the speed factor overrides, except that you cannot specify a tier for a work factor override case. See Configuring speed factors in multiple tier configurations for more information about speed factors. A work factor is in units of millions of CPU clock cycles on a standard kind of machine, and describes the average amount of work that must be done on the managed tier for a single request of that TCM.

Procedure

  1. Reduce the number of back-end nodes in the node group to one back-end node in the node group panel in the administrative console.
  2. Using a workload generator, send traffic to one TCM only. Generate enough traffic to load the back-end node to above 70% utilization.
  3. Record the average values for the steady state throughput and corresponding CPU utilization. You can get those values from the runtime topology view of the admin console. To view the runtime topology, click Runtime operations > Runtime topology.
  4. Compute the work factor value for the transaction class module. Use the value from the following equation:
    work_factor =  (CPU_Utilization * node_speed) / Throughput
    In this case, Node_speed equals the value of the node.speed node custom property. See Configuring node computing power for more information about setting the node.speed custom property. It is assumed that all the nodes in the node group are homogeneous, with equal node speeds.
  5. Compose a string to override the work factor for the deployment target. The pattern defines the set of service classes, transaction classes, applications, or modules that you can override. The pattern is :
    service-class:transaction-class:application:module = value
    You can separate each work factor with a comma, or specify a wild card for any of the variables by using an asterisk. Set the value variable to the computed work factor value. See Autonomic request flow manager advanced custom properties for more information about the grammar for work factor override specifications.
  6. Create the custom property.
    1. Click Custom Properties > New in the deployment target.
    2. Enter the Name of the custom property as workFactorOverrideSpec.
    3. The Value of the custom property is equal to the string composed in the previous step to override the work factor.

What to do next

Configure the speed of the external nodes. See Configuring node computing power for more information.



Related tasks
Configuring the autonomic request flow manager
Configuring speed factors in multiple tier configurations
Routing requests to nodes that are not running WebSphere Virtual Enterprise
Related information
Product overview
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Last updated: Oct 30, 2009 1:33:44 PM EDT
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