File Concepts |
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File Concepts
Defining a file is generally the first step in creating an application.
The standard file format for PROIV is referred to as an internal file format which allows the storage of variable length records and variable length data fields. This minimises disk space and increases flexibility during development since record layout and field length may be modified with minimal impact. PROIV can also access external files.
Files comprise any number of records and each record consists of any number of data items or File Variables as they are termed in PROIV. A File Variable is the smallest unit of accessible data within PROIV.
A file and its associated file variables must be defined before any functions that access that file can be executed. These file variables are the data items that are maintained by the functionality of the system.
In order for functions written in PROIV to store and retrieve information in a physical file, a description of the file and file variables contained in it must be created as a logical file using the file definition and maintenance facility.
The actual data is stored in what is termed the physical file. This file may be held in any of the formats supported by PROIV (for example, C-ISAM, ORACLE). The logical/physical relationship means that each physical file used by PROIV must have at least one logical file definition associated with it.
A file variable must be defined as key or non-key field. PROIV provides two special features which may be applied to key fields.
Topic ID: 730006