Overview of Groups
The basic definitions for group, host, and cluster are the following:
A group is a set of similarly configured hosts within a cluster.
A host is an instance of MarkLogic Server running on a single machine.
A cluster is a set of hosts that work together.
For single-node configurations, you can only use one group at a time (because there is only one host). For clusters configurations with multiple hosts, you can have as many group configurations as makes sense in your environment.
Groups allow you to have several configurations, each of which applies to a distinct set of hosts. Different configurations are often needed when different hosts perform different tasks, or when the hosts have different system capabilities (disk space, memory, and so on). In cluster configurations, a common configuration is to have one group defined for the evaluator nodes (hosts that service query requests) and another group defined for the data nodes (hosts to which forests are attached).
HTTP, ODBC, XDBC, and WebDAV servers are defined at the group level and apply to all hosts within the group. Schemas and namespaces can also be defined at the group level to apply group-wide.
The Configure tab of the Group Administration section of the Admin Interface enables you to define configuration information for memory settings, SMTP server settings, and other configuration settings. The values for the settings are set at installation time based on your system memory configuration at the time of the installation. For a description of each configuration option, see the Help tab of the Group Administration section of the Admin Interface.