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The Data Management Structure: Components and the data structure

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The Data Management Structure: COMPONENTS OF THE DATA STRUCTURE. * DEVICE and DATA FILES: Data sets are objects too. The data base(s) on the AS/400 are divided into so called physical FILES, for want of a better word. Data FILES can be broken MEMBERS for management purposes, but this is not necessary. Typically, if u have more than one type of record in a dataset, you put one type in one file member and another in the other file member in order to keep track of them. "Physical" here means real, live data. This definition is important, because in the AS/400 literature the word FILE is used for many different things. It is a generic word meaning format: The description on the fields of data in a recorder is called a record format, but the congregation of this records-not the data, but the type of format for it-is called a PHYSICAL FILE. Then is the LOGICAL FILE, which takes an entire chapter to describe. Logical file is just a view of data. The AS/400 describes database formats as files. It also calls the devise tables that define how data should be input or output as DEVICE FILES. The editing, sequencing, data checking, and so forth, that needs to be done, says to display output to make it presentable to the terminal operator, and is called a Device Files (presentation management). DEVICE DESCRIPTION is the AS/400 term used to define the fixed, hardware-oriented information the system will use to physically control the device. The Device Files uses the Device description to get the data to and from the hardware device. Another file is the remote system file, called the DISTRIBUTED DATA FILE (DDM). In summary, the AS/400 thinks of databases, devices, and other system as FILES. You define to your system Files that become the doorways to whatever resources you need to talk to or see. You define this file to your system, not to your program, using DDS, a special data definition language. ...read more.


For one, DBMSs improves the availability of data by making the same information easily available to a large number of different users. In the corporate organization example above, all three departments (HR, finance and clinic) would share some common data regarding their members, such as names and identity card numbers. DBMSs also help minimized data redundancy because; generally the information in it appears just once. This can therefore significantly reduce the cost of storing information. DBMSs foster data integrity by allowing updates and changes to the data to be done from one place. The chances of making a mistake are higher if you are required to change the same data in several different places than if you only have to make the change in one place. In our corporate example, when a new employee joins the organization, the HR department might key in his/her particulars in their system and automatically it appears in the finance and clinic databases as well. This reduces repetitive work and increases an organization's efficiency and productivity. We live in any increasing paranoid world. Some types of information in databases are just not meant for any Ali, Ah Kong or Muthu. As such, this information are classified "sensitive" and should be protected or secured and only viewed by select individuals. Through the use of passwords, DBMSs can restrict data access or show only relevant data to those who should see it. Every time you access an ATM facility and punch in your pin number, only information regarding your account is made visible to you - although the ATM might be accessing the same database that has the prime minister's account information in it. This helps improves security and reduces the likelihood of confidential information being view by an unauthorized party. But perhaps the most important advantage of DBMSs is the simplest: it makes using databases a lot easier. Many of today's' DBMSs come with graphical user interface (GUI) ...read more.


Lets see how this can happen. Thousands of web pages these days require you to enter some sort of personal information before you can access their information or services. Among the information most popularly requested is your name and e-mail address. All these names and e-mails are then stored on the web page owner's databases which they use to periodically alert members about new features and services. Although all of the owners of these web pages make solemn promises never to divulge or sell your private information to anyone, more then one dot com has admitted or been caught trying to "share" their members' confidential information with third parties. So as you can see, the issues of privacy and security are real and the legal fraternities of the world are still struggling to address it while at the same time, technology is progressing by leaps and bounds ahead of them. Who should have access to what? With great tools come great risks. As powerful as DBMSs are, they have downsides to their use as well. As a knowledge worker, it is important that you understand the strengths and weaknesses of DBMSs. This will allow you to make better decisions on how to organize and use data and DBMSs. Lets look at some of the risk factors associated with the use of DBMSs. The dollar issue Besides privacy and security, there is also another aspect in using database that's of immediate concern to the user; and that's the cost. Implementing database, especially so in a large environment involves a lot of planning and investment. The cost of training the appropriate personnel itself can be a huge burden to the organization. Often entire network systems need to be set-up just for the database. It is no surprise that many smaller companies are reluctant to implement database on a large scale, preferring to stick to their old "cost-friendly" approach. In time to come, these companies will find it increasing difficult to compete with others that use database technology to deliver products and services to customers. 3 ...read more.

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