Cluster applications

Application resilience is one of the key elements in a clustered environment. If you are planning to write and use highly available applications in your cluster you should be aware that these applications have specific availability specifications.

By taking advantage of resilient applications in your cluster, an application can be restarted on a different cluster node without requiring you to reconfigure the clients. In addition, the data that is associated with the application will be available after switchover or failover. This means that the application user can experience minimal, or even seamless, interruption while the application and its data switch from the primary node to the backup node. The user does not need to know that the application and data have moved on the back end.

In order to achieve application resiliency in your cluster, applications that meet certain availability specifications must be used. Certain characteristics must be present in the application in order for it to be switchable, and therefore always available to the users of the application in the cluster. See High Availability and Clusters for details on these application traits. Because these requirements exist, you have the following options for using a switchable application in your cluster:

  1. Purchase a cluster-enabled software application

    Software products that are cluster-enabled meet certain high-availability requirements.

  2. Write or change your own application to make it highly available

    Independent software vendors and application programmers can customize applications to allow them to be switchable in a IBM® i clustered environment.

Once you have a resilient application, it must be managed within your cluster.