Creating dynamic clusters

When you create a dynamic cluster, weights are used to dynamically balance the workloads of the cluster members, based on performance information that is collected from the cluster members. Creating dynamic clusters enables application server virtualization.

1. Create the dynamic cluster. In the administrative console, click Servers > Dynamic clusters > New.
2. Select the dynamic cluster server type. The dynamic cluster server type determines the type of servers that are members of this dynamic cluster. Depending on the type, you enter the name of the dynamic cluster on this panel or when you select the membership method.
3. For some dynamic cluster types, you can select the membership method. The membership method defines how servers join the dynamic cluster as cluster instances.

   Option	Description
   Automatically define cluster members with rules	You can Automatically define cluster members with rules if you are using servers with complete life-cycle management. With this option, you create a membership policy that defines the nodes on which cluster instances can be placed.
   Manually define cluster members	If you are using servers with assisted life-cycle management, you can Manually define cluster members. With this option, you select existing servers to add to the dynamic cluster. The servers that you select must be homogenous: that is, they must be of the same server type, middleware server version, and have the same applications installed. Note: To add a new middleware server to an existing dynamic cluster when one or more applications are targeted to the dynamic cluster, you must install the applications on the middleware server and target the applications to the server before you add the server as member of the dynamic cluster.

4. Define the dynamic cluster members.
   • If you selected Automatically define cluster members with rules in the previous step, use the subexpression builder to build a membership policy expression for your dynamic cluster. This expression is compared to all the nodes in the cell, selecting any nodes for which the subexpression is true.
   • If you selected Manually define cluster members, the action you take depends on what kind of servers are in your dynamic cluster.
     • If your server type is application server, choose an existing static cluster to convert to a dynamic cluster.
     • If your server type is an externally created middleware server with assisted life-cycle management, select servers from the list, and add them to your dynamic cluster. Before you add assisted life-cycle servers, be sure that they are the same type, middleware server version, and have the same set of applications installed.
       Note: Before you can add a new middleware server to an existing dynamic cluster when one or more applications are targeted to the dynamic cluster, you must install the applications on the middleware server and target the applications to the server.

       1. Deploy your unmanaged application to the middleware server. See Deploying unmanaged Web applications for more information.
       2. Define the deployment target for the application. In the administrative console, click Applications > All applications > unmanaged_app_name. Select the target and click Add.
       3. Click Apply and save your changes.
5. Select a dynamic cluster server template. You can select a dynamic cluster server template only for dynamic clusters that consist of servers with complete life-cycle management. You can choose an existing predefined template, or create your own server templates to use when you create your dynamic cluster. See Creating middleware server templates for more information about creating server templates.
   Note: If your configuration consists of mixed versions of WebSphere Application Server Network Deployment, specifically the deployment manager is at a higher version than the version of the node, you cannot use a predefined server template to create a dynamic cluster. If you are running a Version 6.1 node and a Version 7.0 deployment manager, for example, you can create a static cluster of servers on the node, and then convert the static cluster to a dynamic cluster.
6. Specify dynamic cluster-specific properties.
   1. Define the minimum number of cluster instances. The default minimum number of instances is one instance and the maximum default is no limit on instances. If a minimum value is excessive, performance degradation might occur.
   2. Define the maximum number of cluster instances. The default value has no limit on the number of cluster instances.
   3. Determine whether to enable vertical stacking. When you configure vertical stacking, more than one dynamic cluster instance can start on the same node.
   4. Specify an isolation preference for the dynamic cluster.
7. Confirm the dynamic cluster creation. Click Finish > Save to save the changes to the master configuration.
8. Select the mode of operation. In the administrative console, click Servers > Dynamic clusters. Select the dynamic clusters that you want to modify. Choose the operational mode and click Set mode.
   Important: To use dynamic application placement, click Automatic or Supervised as the mode of operation.

   If you have nodes that run on z/OS® systems, use dynamic clusters in supervised or automatic mode. If you want to prevent WebSphere Virtual Enterprise from automatically starting a cluster member on a logical partition (LPAR) that is hosting a dynamic cluster when the LPAR processor is too busy, then you must define the cpuUtilizationThreshold custom property. In this scenario, the product starts the cluster member only if transaction demand requires additional cluster members and the processor utilization on the LPAR is less than the cpuUtilizationThreshold value. See cpuUtilizationThreshold for more information.