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INTRODUCTION OF DBMS


INTRODUCTION OF DBMS 

    A DBMS is a set of software programs that controls the organization, storage, management, and retrieval of data in a database. DBMS are categorized according to their data structures or types. It is a set of prewritten programs that are used to store, update and retrieve a Database. The DBMS accepts requests for data from the application program and instructs the operating system to transfer the appropriate data. When a DBMS is used, information systems can be changed much more easily as the 
organization's information requirements change. New categories of data can be added to the database without disruption to the existing system. 

    Database servers are computers that hold the actual databases and run only the DBMS and related software. Database servers are usually multiprocessor computers, with generous memory and RAID disk arrays used for stable storage. Connected to one or more servers via a high-speed channel, hardware database accelerators are also used in large volume transaction processing environments. DBMSs are found at the heart of most database applications. 

    The method to enter the large volume of data in a systematic manner with the help of suitable software (generally in the form of table) and getting the required result/data in a defined manner as per requirement without spending the time is called data base management system and the software used to handle this is called DBMS Software's. as for example D base, FoxPro, MS Access, Sybase, oracle, SQL server(structured query language) ,my sql server(open source) 

Logical and physical view 
    A database management system provides the ability for many different users to share data and process resources. But as there can be many different users, there are many different database needs. The question now is: How can a single, unified database meet the differing requirement of so many users? 

    A DBMS minimizes these problems by providing two views of the database data: a logical (external) view and physical (internal) view. The logical view/user’s view, of a database program represents data in a format that is meaningful to a user and to the software programs that process those data. That is, the logical view tells the user, in user terms, what is in the database. The physical view deals with the actual, physical arrangement and location of data in the direct access storage devices (DASDs). Database specialists use the physical view to make efficient use of storage and processing resources. With the logical view users can see data differently from how they are stored, and they do not want to know all the technical details of physical storage. After all, a user is primarily interested in using the information, not in how it is stored.

    One strength of a DBMS is that while there is only one physical view of the data, there can be an endless number of different logical views. This feature allows users to see database information in a more business-related way rather than from a technical, processing viewpoint. Thus the logical view refers to the way user views data, and the physical view to the way the data are physically stored and processed. Features commonly offered by database management systems include: 

Query ability 
Querying is the process of requesting attribute information from various perspectives and combinations of factors. Example: "How many 35 year old radio operators are diploma holder?" A database query language and report writer allow users to interactively interrogate the database, analyze its data and update it according to the users privileges on data. 

Backup and replication 
    Copies of attributes need to be made regularly in case primary disks or other equipment fails. A  periodic copy of attributes may also be created for a distant organization that cannot readily access the  
original. DBMS usually provide utilities to facilitate the process of extracting and disseminating attribute sets. When data is replicated between database servers, so that the information remains consistent throughout the database system and users cannot tell or even know which server in the DBMS they are using, the system is said to exhibit replication transparency. 

Rule enforcement 
Often one wants to apply rules to attributes so that the attributes are clean and reliable. For example, we may have a rule that says each employee of the BSF will have a unique number to identify (identified by regimental Number). If somebody tries to associate a second regimental number with a given employee, we want the DBMS to deny such a request and display an error message. 

Security 
Often it is desirable to limit who can see or change which attributes or groups of attributes. This may be managed directly by individual, or by the assignment of individuals and privileges to groups, or (in the most elaborate models) through the assignment of individuals and groups to roles which are then granted entitlements. 

Computation 
There are common computations requested on attributes such as counting, summing, averaging, sorting, grouping, cross-referencing, etc. Rather than have each computer application implement these 
from scratch, they can rely on the DBMS to supply such calculations. 

Change and access logging 
Often one wants to know who accessed what attributes, what was changed, and when it was changed. Logging services allow this by keeping a record of access occurrences and changes.

 Automated optimization 
    If there are frequently occurring usage patterns or requests, some DBMS can adjust themselves to improve the speed of those interactions. In some cases the DBMS will merely provide tools to monitor 
performance, allowing a human expert to make the necessary adjustments after reviewing the statistics 
collected. 

Examples of Database Management Systems
• Computhink
• Adabas
• Alpha Five
• DataEase
• Oracle database
• IBM DB2
• Adaptive Server Enterprise
• FileMaker
• Firebird
• Ingres 
• Informix
• Mark Logic
• Microsoft Access
• InterSys

Back End-
Where data is stored and managed e.g oracle, sql server, table and queries in access. 

Front End-
This is screen designing area of access to make data presentable for perusal. Front end don’t have its own data .examples are visual basic, d2k Forms and reports in access. 

    Now we will familiarize ourselves with brief introduction of MS access which one of the simplest DBMS software and introduction with the same will give a feel of power and capabilities of DBMS software. 

 Introduction with Microsoft Access Database Fundamentals 
     We are always overwhelmed by the large quantities of data that need to be tracked in our organization? We are currently using a paper filing system, text documents or a spreadsheet to keep track of our critical information. If we want a managed and flexible system for management of this data than MS access is a perfect solution. 

    What is a database? Quite simply, it's an organized collection of data. A database management system (DBMS) such as Access, FileMaker Pro, Oracle or SQL Server provides us with the software tools we need to organize that data in a flexible manner. It includes facilities to add, modify or delete data from the database, ask questions (or queries) about the data stored in the database and produce 
reports summarizing selected contents.


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