A schematic dataset resides in a personal, file, or ArcSDE geodatabase. A set of functions is available in the Catalog window to create and manage schematic datasets.
A schematic dataset in the Catalog tree displays with the following icon 
next to its tree entry.
Because schematic configuration parameters, generated schematic diagrams, and schematic folders reside in a schematic dataset, it is the entry point for your schematic application. Before working with ArcGIS Schematics, you must create a schematic dataset.