The Server mode of the Genomics Server is set in the Job Distribution subsection of the Admin tab.
 

The setting controls whether or not the Genomics Server itself can perform analyses as well as acting as the controlling instance. That is, this option indicates whether users will be able to submit jobs to run directly on the Genomics Server as well as being able to submit analysis jobs to the grid nodes made available via configured grid presets.

If the Server mode is set to MASTER_NODE, the Genomics Server itself will not accept any jobs directly, it will only submit them to the grid system.

If the Server mode is set to SINGLE_SERVER, then the Genomics Server can also accept jobs directly.

Please not that jobs submitted to the Genomics Server itself, rather than to the grid, will only be processed on the Genomics Server. The grid system and the Genomics Server are not considered a single available pool of processing nodes.

In most situations it will be preferable to have the Server mode set to "Master".