Creating a Database

Creating a Database

A Database Definition (DBD) is a text document that describes the database. More precisely, it is called the source DBD.

A source DBD can be created and modified with a text editor. It is saved as a pure ASCII text file, not a word processing file. As a convention, Database Definition text files are stored with extension .dbd.

Refer to the Database Definition document for a description of the Database Definition Language.

Once a source DBD is created and saved, it is compiled with the ddlCompileDBD() function. The compile process analyzes the DBD text and creates the files that contain the database.

A Thunderbolt database consists of 6 principle files, regardless of the number of tables, fields or indexes.

      dbname.ctl   - the object DBD;
      dbname.ddd   - contains data for all tables;
      dbname.ttt   - contains tree structures for all indexes;
      dbname.lll   - contains list structures for all indexes
      dbname.sss   - contains user information;
      dbname.pi    - the object Application Interface

The Application Interface is the external interface to the database. That is, when the database is to be opened, it is the AI that is opened first.

When the source DBD is compiled, a default AI (which is called the General Interface, or GI) is created. The GI is adequate for many applications. If additional control is required, a Custom Application Interface can be created.