The function of the Relativity catalog is similar to that of the "system catalog" in a relational database management system. It serves as a repository for information regarding the structure of relational tables as well as operational information required by runtime components of Relativity, such as the query optimizer. Additionally, the Relativity catalog contains complete information regarding the physical COBOL data file structure (that is, the COBOL file definition, or FD information) and information produced by the database design process (Relativity Designer) that defines the association between COBOL data files and data elements, and the relational tables and their constituent columns. Finally, security information about users, groups, and privileges is stored in the catalog. Together, all of this information allows Relativity to present the COBOL data files through an ODBC interface of an ODBC-enabled application as a relational database of well-normalized tables substantially independent of the original COBOL data file structure of the application.
The Catalog Explorer pane is the focal point in the Relativity Designer main window when a Relativity data source, whose definition specifies the catalog, is opened. Many of the activities related to structuring the COBOL data, so that it can be viewed in a relational table, is performed from here.