what stores metadata instead of actual data in dbms
Metadata repository Each database management system (DBMS) and database tools have their own language for the metadata components within. Database applications already have their own repositories or registries that are expected to provide all of the necessary functionality to access the data stored within. Vendors do not want other companies to be capable of easily migrating data away from their products and into competitors products, so they are proprietary with the way they handle metadata. CASE tools, DBMS dictionaries, ETL tools, data cleansing tools, OLAP tools, and data mining tools all handle and store metadata differently. Only a metadata repository can be designed to store the metadata components from all of these tools.[3]
Database testing White-box testing mainly deals with the internal structure of the database. The specification details are hidden from the user.
Capability Maturity Model Integration Maturity Level 5 - Optimizing
Alonso Álvarez de Pineda