Sample catalog information is furnished with the default AutoCAD Electrical toolset installation. The information is held in tables in a Microsoft Access database file (.mdb), which are populated with sample vendor data. This database can potentially hold hundreds of thousands of entries. Your project likely uses a small percentage of these entries. You can create a project-specific catalog database containing only the entries used in your project.
If you are using Microsoft SQL Server as your primary source for catalog information when working with AutoCAD Electrical toolset, you can still go-ahead and create a project-specific catalog database—the project-specific database created is a Microsoft Access database file (.mdb).