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 product components consume increases nonlinearly 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 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
is the messaging engine that is provided with the product.
WLM uses the high availability manager to both propagate the routing information and make it highly available. Although WLM routing information typically applies to clustered resources, it can also apply to non-clustered resources, such as standalone messaging engines. During typical circumstances, you must leave the high availability manager enabled on any application server that produces or consumes either IIOP or messaging engine routing information.
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.
In a WebSphere Application Server, Network Deployment system, the on-demand configuration is used for IBM WebSphere Application Server proxy server routing. If you want to use on-demand configuration routing in conjunction with your Web services, you must verify that the high availability manager is enabled on the proxy server and on all of the servers to which the proxy server routes work.