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

Policies for service integration

Each messaging engine on a service integration bus belongs to one high availability group. The members of each HAGroup are controlled by a policy assigned to the group at runtime. This policy determines the availability characteristics of the messaging engine in the HAGroup.

If you add a server to a bus, and deploy a messaging engine to the server, the messaging engine can run only on that server. You could configure a non-default policy for the messaging engine but it would not affect the messaging engine's behavior because there is only one server available to it.

If you deploy a messaging engine to a cluster on a bus, you can control which cluster servers the messaging engine can run on by configuring the policy for the messaging engine's HAGroup. You can configure the policy to control whether the messaging engine has a preference for a particular server or set of servers, and whether that preference is enforced. You can also modify the policy to change the monitoring interval for the messaging engine.

The following table shows the types of policy you can use for messaging engines, and how each type affects the behavior of a messaging engine that belongs to a cluster bus member.
Policy type Behavior
Static The messaging engine is restricted to a particular server. The messaging engine can run only on the server to which it is restricted, and cannot failover to any other server in the cluster. If you have multiple messaging engines this can be a useful configuration for workload sharing where failover is not wanted.
One of N with no preferred servers The messaging engine can failover to any of the other servers in the cluster, and has no preference for any particular server.
with preferred servers The messaging engine can failover to any of the other servers in the cluster, but will run on the most preferred server that is available at the time the messaging engine is activated . You can add more than one preferred server if required; placing a server earlier in the list indicates a stronger preference for that server. The messaging engine will not be moved automatically to a server that appears earlier in the list, if that server becomes available.
with preferred servers and the Fail back setting The messaging engine can failover to any of the other servers in the cluster, but will always run on the most preferred server that is available. You can add more than one preferred server if required; placing a server earlier in the list indicates a stronger preference for that server. The messaging engine will be moved automatically to a server that appears earlier in the list, if that server becomes available.
with preferred servers and the Preferred servers only setting The messaging engine can failover to any of the preferred servers in the cluster and cannot run on a server that is not in the set of preferred servers. You can add more than one preferred server if required; placing a server earlier in the list indicates a stronger preference for that server. You can use the Fail back setting in conjunction with Preferred servers only; this causes the messaging engine to be moved automatically to a server that appears earlier in the list, if that server becomes available.
No operation

The messaging engine is managed by an external high availability framework and can failover to any of the other servers in the external high availability cluster. If a server affinity is required it should be configured as a preference in the high availability cluster configuration. The configuration details depend on the choice of high availability framework.

This policy is useful where a high availability clustered database is being used for the messaging engine's data store; it allows you to put the messaging engine under the control of the same high availability cluster that is managing the database. This policy is also useful where a messaging engine is connected to a WebSphere MQ Queue Manager; the messaging engine can failover if it is using a high availability clustered IP address for its inbound channel chains. For more information, see External high availability frameworks and service integration.

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Related tasks
Configuring a policy for messaging engines

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Last updated: 5 Oct 2005
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