1. File Processing vs Database Processing
  2. and Metadata


File Processing

The concepts involved in File processing are more closely related to computer programming than database design. The very first efforts in data storage involved writing to files from a program. If you have every done any file i/o using a computer program, you have experienced the concept of file processing.
There are several good links available in todays assignment that should give you a good understanding of what exactly is involved in File Processing from a data perspective. Basically we write data to files in a structured way and retrieve data from the file in the same way. The files are normally sequential (records must be processed one after the other) so the process can be very time consumeing on large files.
Several companies still use this form of file processing and its associated "transaction processing" schemes. First Data, Mutual of Omaha are two that are pretty prominent.
Basically, in file processing, we create a structure to contain the data, the structure is designed in such a way that data can be written to memory and read from memory in a fixed way. These structures are normally referred to as records when they contain data. Here is a link to a cobol program that defines a record in the data division. This program can read data from this structure but no others. As you can see this program reads data from a StudentFile that has several elements contained in it. This file is or can be unique to this program. So if another program wants to write to the file, it may create duplicate data without knowing it. The data is not always checked for duplicates.



As you probably have seen from the links provided, the concept of metadata is fairly straigt forward. Its simply data about data. In more simplistic terms, its information that describes the fields of data that we want to store. For example, if I want to store a name, I need to know how long the name is or will be and what type of data it is. Most names are collections of characters, so the metadata for a name field would be something like this:
collection of 25 letters (a string). I might go on to say that the name cannot be null, and it must contain at least 5 letters. These are all data about data or information describing the field name. There are several good links available in todays assignment that should give you a good understanding of what exactly is involved in metadata
The cobol program we looked at in the last section has a good example. Here is a link to a cobol program . Notice under the DATA DIVISION the section that describes the record the program reads. Notice the 'pic' statements after the fields, these are a form of metadata for the program. They tell the program how to display the data elements it will read.