4.2 Clustering OpenVMS Galaxy Instances Instances in an OpenVMS Galaxy computing environment can be clustered with other instances in a single system, with instances in other Galaxy systems, or with non-Galaxy systems. Each type of clustering has different licensing requirements, as described in the following sections. 4.2.1 Clustering in a Galaxy System In an OpenVMS Galaxy computing environment, instances can be clustered with other instances within a Galaxy sys- tem. Clustered instances use the shared-memory cluster interconnect to communicate with each other. The licensing and functionality for clustering within a Galaxy system is provided under the OpenVMS Galaxy License. 4.2.2 Clustering Outside a Galaxy System Instances in an OpenVMS Galaxy computing environ- ment can be clustered with instances in another OpenVMS Galaxy system or with cluster nodes in non-Galaxy systems. Instances clustered outside of a Galaxy system use traditional cluster interconnects. Each system that is clustered with another system must be licensed for OpenVMS Cluster Software. Clustering outside the OpenVMS Galaxy system is not covered by the OpenVMS Galaxy License.