WebSphere Application Server V8.5 Administration and Configuration Guide for the Full Profile

646 WebSphere Application Server V8.5 Administration and Configuration Guide for the Full Profile

18.1 Clustering on z/OS systems

Clustering technology is an integral part of WebSphere Application Server for z/OS V8. In this

section, we provide information about the concept of clustering and how to create a cluster on

z/OS systems.

18.1.1 Clustering for scalability and failover

Clustering as a high availability approach is used extensively in WebSphere Application

Server to provide for scalability and failover protection at the same time. A

cluster consists of

multiple copies of the same component with the expectation that at least one of the copies will

be available to service a request. In general, the cluster works as a unit where there is

collaboration among the individual copies to ensure that the request can be directed toward a

copy that can service the request.

A WebSphere Application Server cluster is composed of individual cluster members, with

each member containing the same set of applications. In front of a WebSphere Application

Server cluster is a

workload distributor that routes the workload to individual members. z/OS

Workload Manager (WLM) assigns system resources to units of work from the workload,

making a best attempt to allow all work to meet the specified goals.

Clusters can be vertical within an LPAR (that is, two or more cluster members residing in the

same z/OS system), or they can be placed horizontally across LPARs on different machines

to obtain the highest availability in the event that an LPAR or machine that contains a member

has an outage. In a vertical cluster, the servers compete with each other for resources.

For more information about clustering in WebSphere Application Server for z/OS V8, go to the

following website:

http://pic.dhe.ibm.com/infocenter/wasinfo/v8r5/index.jsp?topic=%2Fcom.ibm.webspher

e.zseries.doc%2Fae%2Fcrun_srvgrp.html

18.1.2 Creating a cluster on a z/OS system

To create a WebSphere Application Server for z/OS cluster:

1. Click Servers  Clusters  WebSphere application server clusters.

2. Click New in the WebSphere Application Server clusters view, as shown in Figure 21-1.

Figure 18-1 WebSphere application server clusters view

Chapter 18. Clustering and high availability 647

3. Enter basic cluster information, as shown in Figure 21-2. If you are converting an existing

application server into the cluster, leave the Short name field empty to default to the

generic short name of that application server. Click Next.

Figure 18-2 Enter basic cluster information

4. Create the first cluster member. In the Select basis for first cluster member section, select

Create the member by converting an existing application server, as shown in

Figure 21-3. Click Next.

Figure 18-3 Create first cluster member

648 WebSphere Application Server V8.5 Administration and Configuration Guide for the Full Profile

5. Add additional cluster members by specifying the member name and short name. Click

Add Member, as shown in Figure 21-4. Click Next.

Figure 18-4 Create additional cluster members

Chapter 18. Clustering and high availability 649

6. Review your setup in the summary, and click Finish, as shown Figure 21-5.

Figure 18-5 Summary

7. Click Review, click Synchronize changes with nodes, and click Save. Alternatively, click

System administration  Nodes, and click Synchronize with the appropriate node or

nodes selected, or enable the Synchronize changes with Nodes option in System

administration  Console Preferences.

8. Restart the converted application server by clicking Servers  Server Types 

WebSphere application servers.

Replication note: When you select HTTP replication, a replication domain of the same

name as the cluster name is created automatically with a Single replica option.