Designing the File or Database

The objectives in the design of data storage organization are:

• The data must be available when the user wants to use it.
• The data must be accurate and consistent.
• Efficient storage of data as well as efficient updating and retrieval
• It is necessary that information retrieval be purposeful.
• The information obtained from the stored data must be in an integrated form to be useful for managing, planning, controlling, or decision making.

There are two approaches to the storage of data in computer-based systems. The first method is to store the data in individual files, each unique to a particular application. A file can be designed and built quite rapidly, and the concerns for data availability and security are minimized. Also, systems analysts can choose an appropriate file structure according to the required processing speed of the particular application system. The second approach to the storage of data in a computer-based system involves building a database, which is a formally defined and centrally controlled store of data intended for use in many different applications.

The effectiveness objectives of the database include:

• Ensuring that data can be shared among users for a variety of applications
• Maintaining data that are both accurate and consistent
• Ensuring all data required for current and future applications will be readily available
• Allowing the database to evolve and the needs of the users to grow
• Allowing users to construct their personal view of the data without concern for the way the data are physically stored

Keys are data items in a record that are used to identify the record. Key fields are used for record retrieval (lookup). There are different types of keys:

• Primary Key. Uniquely identifies a record.
• Secondary Key. May not be unique.
• Concatenated Key. The key consists of a combination of two or more fields.
• Foreign Key. A field in one record that is the key of another record. Used for linking a record in one file or table with a record in another file or table.

A file contains groups of records used to provide information for operations, planning, management, and decision making. Files can be used for storing data for an indefinite period of time or they can be used to store data temporarily for a specific purpose. A master file contains records with all pertinent information about an entity. A transaction file contains the detail records representing individual transactions. Transactions records may be used to update a master file.

A database is intended to be shared by many users. Different users may see the data in different ways (i.e., have different views of the data). Data needs to be stored only once for several applications. This implies cost efficiency in terms of storage space and maintenance.