A high availability manager consumes valuable system resources, such as CPU cycles, heap memory, and sockets. These resources are consumed both by the high availability manager and by product components that use the services that the high availability manager provides. The amount of resources that both the high availability manager and these WebSphere Application Server components consume increases exponentially as the size of a core group increases.
For large core groups, the amount of resources that the high availability manager consumes can become significant. Disabling the high availability manager frees these resources. However, before you disable the high availability manager, you should thoroughly investigate the current and future needs of your system to ensure that disabling the high availability manager does not also disable other functions that you use that require the high availability manager. For example, both memory to memory session replication, and remote request dispatcher (RRD) require the high availability manager to be enabled.
The capability to disable the high availability manager is most useful for large topologies where none of the high availability manager provided services are used. In certain topologies, only some of the processes use the services that the high availability manager provides. In these topologies, you can disable the high availability manager on a per-process basis, which optimizes the amount of resources that the high availability manager uses.
Do not disable the high availability manager on administrative processes, such as node agents and the deployment manager, unless the high availability manager is disabled on all application server processes in that core group.
Some of the services that the high availability manager provides are cluster based. Therefore, because cluster members must be homogeneous, if you disable the high availability manager on one member of a cluster, you must disable it on all of the other members of that cluster.
Memory-to-memory replication is a cluster-based service that you configure or enable at the application server level. If memory-to-memory replication is enabled on any cluster member, then the high availability manager must be enabled on all of the members of that cluster. Memory-to-memory replication is automatically enabled if:
Singleton failover is a cluster-based service. The high availability manager must be enabled on all members of a cluster if one or more instances of the default messaging provider are configured to run in the cluster. The default messaging provider that is provided with the product is also referred to as the service integration bus.
Workload management (WLM) propagates routing information for the default IBM Java Messaging Service (JMS) provider, which is also referred to as the messaging engine.
When the servlet in cluster 2 calls the enterprise bean application in cluster 1, the high availability manager must be enabled on all servers in both clusters.
Workload management provides an option to statically build and export route tables to the file system. Use this option to eliminate the dependency on the high availability manager. See Enabling static routing for a cluster for more information about the Export route table option.
In a Network Deployment system, the on-demand configuration is used for proxy server routing. If you want to use on-demand configuration routing in conjunction with your Web services, you must make sure that the high availability manager is enabled on the proxy server and on all of the servers to which the proxy server will route work.