A single DMSUPPORT library can be used for more than one database. This DMSUPPORT library maintains more than one set of data files. The structures in each database that share a common DMSUPPORT library must be the same; their items and formats must also be the same. Common applications for this facility are test and production databases or the division of a database containing large amounts of data in several parts. The databases are permitted to differ in certain respects, as discussed in the following text. The process of creating and describing databases that share a DMSUPPORT library is referred to as modeling.

When modeled databases are used, application programs can run against any of the databases interchangeably. This use of modeled databases is accomplished with the database equation, which is described fully in the Application Program Interfaces Programming Guide. The database title can be given at program compilation time or at program run time. Thus, the same object program can use any member of the family of databases by specifying the appropriate title. On another run, the object program can use a different database-family member or the same one again. In general, programs need not be recompiled to be converted from test to production mode.