Registry tables are an optional feature of SuperCHANNEL that you can use to simplify the process of designing target SuperSTAR databases.
By creating registry tables in your source database, you can give SuperCHANNEL additional information about your source data. The more information you put into registry tables, the less work you need to perform designing the target database in the SuperCHANNEL GUI.
For example, you can use them to tell SuperCHANNEL which source tables are the fact tables, which are the classifications, and how the classifications relate to the fact table columns. SuperCHANNEL can then use this information when it creates your output SXV4 database, without you having to manually define the relationships in the SuperCHANNEL GUI.
Registry tables are particularly useful in a scripted database building environment. If you are writing code to perform some of your ETL (Extract-Transform-Load) work, then you can have your program also create and populate the registry tables (defining the table joins and other rules). That way, your entire database build process, from source data to SXV4, can be automated under program control, without needing to manually define the star schema in the SuperCHANNEL GUI.