WebSphere WebSphere Application Server Network Deployment, Version 6.0.x Operating Systems: AIX, HP-UX, Linux, Solaris, Windows

Configuring a One of N policy for service integration

Use this task to continue the configuration of a One of N messaging engine policy.

Before you begin

To complete this task you must have first completed the steps in Configuring a policy for messaging engines.

Why and when to perform this task

A One of N policy can be used to run a messaging engine in a cluster to provide a failover capability. One cluster server runs the messaging engine whilst the remaining cluster servers act as standby servers, ready to run the messaging engine should it no longer be able to run in its current server. This type of policy can also manage a messaging engine running in a server bus member, however this is equivalent to a cluster with only one server (in other words the value of N is 1), and does not provide failover.

Steps for this task

  1. If required, define one or more preferred servers:
    1. Click Servers > Core groups > Core group settings > coregroup_name > Polices > policyname > Preferred servers.
    2. Select the servers you require from the left hand pane and add them to the right hand pane.
    3. Adjust the order of your list as required. If you specify multiple preferred servers the order in which they are specified is important. There is an implicit stronger preference for a server that appears earlier in the list.
    4. Click OK.
    Defining preferred servers specifies that the messaging engine should run in one of the cluster servers that is preferred over the others. This can be used to help spread workload across the cluster, or may be necessary if one server has more resources available to it or typically performs less work than the others.
  2. If required, restrict the messaging engine to run only on preferred servers, by selecting the Preferred servers only check box. The messaging engine will now be incapable of running on a server that is not in the preferred servers list.
  3. If required, specify that the messaging engine should automatically fail back to a preferred server, by selecting the Fail back check box. When the messaging engine is not running on one of its preferred servers, it will now automatically move back to one of its preferred servers if one becomes available. In addition, if the messaging engine is running on a preferred server, and a server which appears earlier in the preferred servers list becomes available, the messaging engine will be automatically moved to that server.
  4. Ensure that the messaging engine can always reach its data store. If the messaging engine is configured to be able to failover then its data store must be accessible from any server in the cluster on which the messaging engine may run. The set of possible servers depends on whether you have configured preferred servers and whether you have set the Preferred servers only option. For example, suppose you have a cluster of three servers, server1, server2 and server3, containing a messaging engine using a policy that allows it to fail over to any of the servers in the cluster. The data store for the messaging engine must be accessible from all three servers. If however you configure the messaging engine's policy with preferred servers server1 and server2, and set the Preferred servers only option, then only server1 and server2 would need access to the data store for that messaging engine.
  5. If required, alter the isAlive health monitoring interval. This determines the frequency with which the HAManager checks that a messaging engine is running properly. The default is 120 seconds.
  6. Click OK.
  7. Save your changes to the master configuration.
Related concepts
Service integration high availability and workload sharing configurations

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Last updated: 15 Mar 2007
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