The large-scale database was developed by IBM. It has two database types; one is a relational database, a typical representative product: DB2; the other is a hierarchical database, a representative product: IMS hierarchical database.

The data definition of large databases includes database schema definition and foreign schema definition. The database schema of a large database is a collection of physical database record types. Each physical database record type corresponds to a hierarchical schema in the hierarchical data model and is defined by a DBD. The mapping of the physical database record type to the storage database is contained in the DBD definition of the physical database record type.

The external schema of a large database is a collection of logical database record types. Each logical database record type is defined by a PCB. The mapping of a logical database record type to a large database schema is contained in the PCB definition of the logical database record type. Users manipulate data according to external schemas.