Configure vertical stacking

Operating Systems: AIX, HP-UX, Linux, Solaris, Windows, z/OS

Configure vertical stacking

You can configure vertical stacking to enable the application placement controller to start more than one instance of the dynamic cluster to improve bottleneck conditions within an application.

Before you begin

Vertical stacking is supported on the z/OS^® operating system, but the WebSphere^® Application Server for z/OS multiple servant feature is the preferred alternative. Consider using vertical stacking for application servers on the z/OS operating systems only for application servers that host applications that are constrained to run in a single servant application server.
To use vertical stacking, the nodes in your dynamic cluster must be at the same product version as the deployment manager, or at a later version. Nodes that are at an earlier release than the deployment manager cannot start multiple server instances on the same node.
Vertical stacking can occur only on nodes that have complete life cycle management. You cannot configure vertical stacking for dynamic clusters that have manually defined cluster members.

About this task
Use vertical stacking to improve bottleneck conditions in your application. With vertical stacking, multiple server instances can start on a node. By configuring multiple server instances, you can use all the power that is available on the nodes when a large workload exists for the application.

Procedure

Determine whether your application has an internal bottleneck by profiling the application. The application placement controller assumes that the only resource bottleneck that an application might have is either in the processor or in memory. Otherwise, the application might have an internal bottleneck.

Run an instance of the application on each node.
Increase the load for the application.
Use the runtime reports, the throughput curve and processor utilization on a node that is running the application. Click Runtime operations > Reports.
If the throughput curve saturates while increasing the load, but the processor utilization remains well below 100%, the application might have an internal bottleneck. Configure vertical stacking to improve these bottleneck conditions. If the server instances are able to reach processor utilization near 100%, do not enable vertical stacking.
Determine the appropriate stacking number. The stacking number is the number of application servers for a cluster that are needed to use all the power of a node. For more information about determining a stacking number, see Determining the stacking number for a dynamic cluster.
Enable vertical stacking and the stacking number. If your dynamic cluster is deployed to a node group that has homogeneous nodes, you can configure the stacking number one time in the administrative console. If your dynamic cluster is deployed to a node group that has heterogeneous nodes, configure the stacking number by specifying custom properties.

To enable vertical stacking for a dynamic cluster that is on homogenous nodes, see Configure a dynamic cluster with homogeneous nodes to support vertical stacking.
To enable vertical stacking for a dynamic cluster that is on heterogeneous nodes, see Configure a dynamic cluster with heterogeneous nodes to support vertical stacking.

Results
When a large workload exists, the application placement controller can fully use the power of the nodes by starting multiple cluster instances on each node.
The general formula to determine the percentage of the processor that is used by each instance on a node is 100%/maximum_number_of_stacked_instances. For example, if three instances are stacked, then workload is throttled to prevent any one of these instances from using more than 33% of the processor.

What to do next
Tune and monitor your application placement configuration.

Subtopics

Determining the stacking number for a dynamic cluster

Configure a dynamic cluster with homogeneous nodes to support vertical stacking

Configure a dynamic cluster with heterogeneous nodes to support vertical stacking

Next topic
Monitor and tuning the application placement controller

Related concepts

Dynamic clusters

Related tasks

Deploying enterprise applications Creating dynamic clusters

Related reference

Static clusters versus dynamic clusters
Related information

Application placement custom properties