2-01:Fields

Chapter 2-1: Data Dictionary Overview

Fields

Fields represent the smallest unit of data storage in an APPX application. Each field contains an item of alphanumeric, numeric, date/time, or logic information in a database (field types are described in detail in the following section). While a domain establishes physical storage requirements and various attributes for a field, it is a field itself that actually stores application data. The data information stored in a field is referred to as a field value. For example, a telephone number domain may specify a length of ten alphanumeric characters to store. It is a template for all telephone number fields in the database that reference it. But, it is not until a customer telephone number field is actually created in the database management facility that APPX allocates storage space. The customer's telephone number would be stored in this field in, say, the customer record.

The relationships between various fields in a database are established in APPX files. The fields defined for a file in the data dictionary determine the record layout of the file.

With a few exceptions, APPX fields are database-dependent (unique to a specific database). Work fields and fields that are not stored in permanent, disk-based files are database-independent. Refer to Temporary versus Permanent Files in this chapter and Integration with Database Management and System Administration in Chapter 2-2, for more information on database dependency.

APPX Application Design Manual (01/13/03)