You can modify the values for several of the extension properties in the Instant Messaging RTR file (SUNW.iim) to configure your HA environment. Extension properties are properties that are specific to the resource type. These properties are inherited by every resource of the same type. Instant Messaging extension properties are described in Instant Messaging RTR File Parameters.
See the documentation for rt_reg and property_attributes in the Sun Cluster Reference Manual for Solaris OS for more information on the contents of resource type registration files and instructions on customizing values for extension properties.