Database File Hierarchy

The file hierarchy on a database consists of four levels:

1. The SYSTEM file. A dictionary file that contains definition items for all accounts on this database and for accessible remote databases.

2. Master Dictionary (MD) file: one for every account on the database. Each MD includes some of the following:

   • D-pointers to the dictionaries of user files on that account.
   • Q-pointers (synonym pointers) to other user files on this or another account or another database.
   • Command definitions that can be used when logged-on to this account.
   • Definitions for English connectives.
   • Default data definition items.

3. User file dictionaries. These contain items with the names of the associated data sections, index definition items, and data definition items which define the contents of data section items that are accessed via English.

   User file dictionaries that are dictionary-only files can also be defined at this level.

4. Data sections consisting of user-defined items.  Each item contains 'attributes' that are the actual data.

This hierarchy of files is shown in the diagram below.

For information on creating Q-Pointers and for general information about file structures, see File and File Index Management and File and Item Structures.