DBMS packages-4

Today we continue our discussion on DBMS Packages. Software packages called Data Base Management System (DBMS) has been developed long before micro-computers to handle the problems of maintaining and integrating large volumes of data on large machines. The most important distinguishing feature of a DBMS package on personal computers is that it provides a very high level language interface which can be learned by a user who is not a computer programmer. We have already talked some important command in our previous post. Today we will talk on other command like quit, use custlist etc….

 

..QUIT

Next day when we start the dBASE III programme, we must first indicate which file we want to use, otherwise dBASE III will not know which file we are interested in. The command for this is

 

..USE CUSTLIST

Now let us say we want to query on the customer data for extracting different types of information. Here is a sample list to illustrate how easy it is. 
 

One has to learn only few additional features to see how sales and receipt transactions can be used to update amount due for each customer. The dBASE III package also has REPORT command for producing user specified reports. With the command verbs, dBASE III also provides conventional programming features like IF-THEN-ELSE, WHILE-DO. A complete set of dBASE III programmes can be designed to implement a medium sized application in a couple of weeks.

 

DBMS packages-1

Each record will have to contain details about a customer. What constitutes ‘the necessary details’ will depend mostly on what use we want to make to this data-base. When we create a customer file through dBASE III package, it will first want us to specify the record structure for the file. For a blinds company who are selling vertical blinds, roman shades products online. When they are creating their DBMS file, their criteria is different than for the company who are providing instant life insurance rates and life insurance quotes online.

 

For a customer file we want each record to have nine fields: one each for the items listed above. In dBASE III, it is necessary to give names to each of these nine fields so that they can be later referred to using these names. The field names which we have chosen are shown in the third column above. Apart from the name, we have to also indicate what type of data will be stored in the field and in certain cases number of characters to be reserved to hold the data for that field. We will want AMOUNTDUE and CRDLMT to hold numeric data and all other fields to hold text or character data. Now let us have a quick look at a dialogue in dBASE III for creating and using such a file.

DBMS packages

In our last post we have discussed on Data Base Management System (DBMS) and today we are going to talk on DBMS packages.

 

Like other DBMS packages, dBASE III provides features for: 

1.      Creating data files on a computer.

2.      Maintaining these data files by way of providing functions for adding, deleting editing and updating a give set of data items.

3.      Generating reports based on the data files created through dBASE III

4.      Querying on those data files.

 

To develop an understanding of the features provided by dBASE III package, let us take a specific application and see how it could be implemented in dBASE III. Suppose we are operating a small business house which has 1000 customers. We are interested in maintaining a list of these customers and using this list for our day-to-day business operations. Obviously we will have to create a file which contains data about these 1000 customers. In this file there will be one record for each customer. Thus, we will have a file containing 1000 records.

Operating Systems-1

We are talking computers in management. We talked evaluation of computers and computer softwares in our previous talk. We talked about operating system in our last post, today we continue with that. We talked the drawback of idling the CPU was overcome with the introduction of overlapped processing.

For example why not take up input operation of job 2 and the output operation of job 1 simultaneously? This and similar considerations gave rise to the concept of multi-programming. A multi-programming operating system handles multiple jobs simultaneously by overlapping the input, output and processing cycles of various jobs.

This operating system was introduced along with third generation computers and is still very popular. It has replaced the earlier batch processing (serial) operating system. With multi-programming a CPU’s utilization is increased and hence jobs get executed faster on an average. However a multi-programming operating system is more complex hardware to support it.

Other types of operating systems which are popular today are multi-processing operating systems and real time operating systems. A multi-processing operating system uses multiple CPU’s to process multiple jobs. A real time operating system is a very different type of operating system, because it is used for different type of applications, i.e., real time applications such as airlines reservations, process control, etc.

Utilities

Utility programmes are those which are very often requested by many application programmes. mailing leads and marketing list are few example of such utility programmes which are used in large by industry. A few examples are:

SORT/MERGE for sorting large volumes of data and merging them into a single sort list like mortgage mailing list.

Transfer programmes for transforming contents from one medium to another, e.g., disk to tape, tape to disk, etc.

Magnetic Disk-1

Last time we talk about magnetic tape. Today we are going to discuss on Magnetic Disk which is important device and part of the computer hardware. Magnetic disk was invented to overcome the sequential processing requirement of magnetic tape data. It is helpful to visualize a magnetic disk as a LP record. An access mechanism moves the read/write head to the desired surface on the disk to provide random access of data. A disk pack is a collection of individual disks stored vertically one atop the other and mounted on a disk drive. The disk drive rotates the disk pack at a constant speed. There is enough room in between the spinning disks to allow access arms with read/write heads to move to any storage location.

 

Each disk in a disk pack has two recording surfaces, except the first and last disks which have only one recording surface. Thus a disk pack with 10 disks provides 18 recording surfaces. Such a disk pack also has 9 access arms. Each access arm supports two read/write heads, one read/write head to access the lower recording surface of the top disk and the other read/write head to access the upper recording surface of the bottom disk.

Magnetic Tape

As a part of our talk on computer management, today we are going to talk about Magnetic Tape. A magnetic tape is very compact medium for storing a large amount of data. A standard tape reel is 2400 feet long, ½ inch wide and can store up to anywhere from 20 MB to 150 MB depending on the recording density it permits. A magnetic tape is mounted on a tape drive which has a read/write head. ISP or hosting service provider provides managed hosting services. Data stored and data management is handled by data center.

The density of a magnetic tape refers to the amount of information stored in one inch of its tape length and is measured in bits per inch (bpi). Standard tapes come with 800 bpi or 1600 bpi, even though tapes with 6250 bpi are also common. A text book of 600 pages with 50 lines per page and 40 letters per line can be accommodated in less than 20 feet of a tape of density 6250 bpi. Imagine how much data can be stored in a 2400 feet tape? These technologies can store huge volume of data in small amount of space, same time the risk of data lost also increase. When planning is going on for data stored or data management, management needs to plan about disaster recovery. Data safety and data recovery is very much important for any computerize management system.

The major advantage of a tape is its economical storage of large volumes of data and a quick transfer of its contents to CPU. However it has a major disadvantage namely it permits only a serial access of data. This is because the read/write head is fixed and immovable. As a result the tape has to be moved physically over the read/write head till we come to the desired location to access the required data.

Managerial Participation

The Single most critical problem in effective computer utilisation is the meet for understanding and support form top management. In a State like Andhra Pradesh, the Chief Minister’s personal encouragement has paved the way to bring computerised MIS gradually to all the districts, apart from their wide-spread use in State departments and in the Secretariat. 

 

Even after top management support is ensured, it is necessary that there is user participation in the design phase on corporate MIS so as to avoid subsequent extensive and time-consuming re-work. This can be called “overnight syndrome” where user spell out there needs and expect the computer professionals to deliver the outputs immediately thereafter. Like solvent recyclers works.Converting jobs eventually for computerisation needs a stabilisation period, which is all too easily forgotten

 

An example of the above is the case of Utter Pradesh State Electricity Board which went for computerised electricity billing for the Western districts. In the design phase, the Board authorities dictated that only Agra and Ghaziabad should have a pilot project before its extension to all other districts. Also, manual financial ledgers for at least two billing cycles so as to generate enough confidence in the computerised ledgers. The result was a smooth introduction of computerisation. On the other hand, another State Electricity Board went through a similar computerization process without the benefit of any pilot project or parallel run on the grounds that the results were needed fast and they were spending money on computers in any case. We need to use solvent recycler before we use any other liquid, other wise output will be different. 

 

The consequence was a disaster when many erroneous bills came and in some cases none at all. There were questions in the Parliament and an enquiry committee under the Central Electricity Authority had to investigate the mistakes. The result was to cancel the existing computerisation, to start de novo, after having spent several lakhs of rupees which went waste. In case of chemicals, we need to do solvent recycle before we do any process, same way we need to  check it with manually as well as compurerisation together for sometime

 

It makes good sense, as has been experienced in the NTPC, when the user-manager picks up a minimum familiarity with the MIS at the beginning. From the point of view of the organisation, corporate MIS is as much a vital part of the operation as marketing operations and finance are today. Indian Airlines, too, discovered that mangers had to be involved in order to get better and more effective information systems by virtue of their participation. A similar approach is being followed in LIC.

 

 

Lack of good Management System

It is imperative for successful corporate MIS on computer that there is good planning and control within the framework of an efficient organisational structure. No degree of sophistication with computers can cure the basic ill of chaotic data management.

 

There have been many organizations where computerization has not brought any tangible improvements because there has been no systematic handling of data or attention paid to the data management. In such cases, there would have been considerable gain by first conducting a good Organisation and Method (O&M) study. MIS has to be built on top by a management system which should include the organisational arrangements, the structure and procedures for adequate planning and control, the clear establishment of objective, and all other manifestations of good organization in management.

 

It is interesting to note that good computer professionals know their craft but are simply not oriented to managerial jobs. In other words, the broad-based skills, which are necessary to function both in the computer room and in meeting with user-manager for the MIS, are conspicuous by their absence. This phenomenon has been known globally and that is why computer professionals are often called ‘machine-mesmerised’, where they are more loyal to their profession than to their organisation!