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Chapter 7

Information SystemData Management

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File Processing Files consist of related records. Records consist of related fields. Fields consist of related

characters. Files must contain a key field

(primary key) – a field where each record’s occurrence is unique.

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File Organization A file can be organized in secondary

storage as a: Sequential file – records are organized one

after the other and can be accessed sequentially (based on the value of the primary key). In order to retrieve a record, each record must be examined until the desired record is located.

Direct or Random file – records are not necessarily stored in sequence and can be accessed directly.

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File Organization (cont’d.) A file can be organized in

secondary storage as a: Indexed file – records are stored in

one file and the organization of those records is stored in a second file. To use an indexed file both files, the data file and the index file, must be used together.

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File Management Managing data files requires that

the data be kept up to date. To do so requires: Modifying, or updating, records

involves Adding records Deleting records Changing records

Data Validation – ensuring the data is accurate (up to date) and secure.

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Advantages and Disadvantages of File Processing Advantages:

Easy to use. Disadvantages:

Data redundancy or duplication of data (updating).

Difficult to access data from more than one file at a time.

Dependency between programs and data.

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Database Processing To overcome some of the

disadvantages of file processing, database processing is used instead.

The database software is called a DataBase Management System (DBMS).

A database is a collection of data and relationships between data stored in secondary storage.

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Data Relationships One-to-one relationship

One group of data is related on only one other group of data. For example, the relationship between customers records to an account receivable record are one to one)

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Data Relationships One-to-many relationship

One group of data is related to one or more other groups of data. For example, the relationship between customers records to sales order records are one to many.

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Data Relationships Many-to-many relationship

One or more groups of data is related to one or more other groups of data. For example, the relationship between Inventory records and suppliers records are many to many.

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Advantages and Disadvantages of Database Processing Advantages:

Duplication of data is reduced. Easier to process different groups of

data. No dependency between data and

programs. Disadvantages:

Expensive. More vulnerable than file processing. Can be complex to develop.

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Types of Databases Hierarchical database Network database Relational database

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Types of Databases Personal databases are generally

used by only one person. Shared databases are used by

many users at one time. To prevent users from accessing

data they do not need, the database is divided into views (Sub-schemas).

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Data Warehouses A data warehouse is a collection of

data drawn from other databases used by the business.

A data mart represents the specific data from a data warehouse which a user needs.

Data mining is the technique of searching for patterns in the data.

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On-Line Analytical Processing On-Line Analytical Processing

(OLAP) permits users to “slice and dice” large amounts of data in databases, data warehouses, and multidimensional databases using a variety of techniques, including statistical techniques.

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Database Administration An organization with large

databases often has a Database Administrator (DBA) who is responsible for managing the organization’s database.

The DBA designs the databases based on the needs of the users.