Introduction to Database Management System
DBMS stands for Database Management System, so let us break down the words what they really mean. A database is a place where we store, retrieve and manage data. So what’s a data then? Meaningful information like your name, your favorite color etc to complex data like astronomical data that scientist handle, everything comes under database. The management system refers to a set of programs to manage the data, we have with various actions like storing, retrieving, filtering etc. Some of the popular Database Management System is MySQL, Oracle etc. Giving protection to data, user-friendly for users etc, are some of the notable features of good DBMS.
Definition: “A database management system (DBMS) is system software for creating and managing databases. The DBMS provides users and programmers with a systematic way to create, retrieve, update and manage data.”
In a database, we would be grouping only related data together and storing them under one group name called table. This helps in identifying which data is stored where and under what name.
The concept of storing the data started before 40 years in various formats. In earlier days they have used punched card technology to store the data. Then files were used. The file systems were known as predecessor of database system. Various access methods in file system were indexed, random and sequential access. The file system had more limitations like
Data Duplication – Same data is used by multiple resources for processing, thus created multiple copies of same data wasting the spaces.
High Maintenance – Access control and verifying data consistency needs high maintenance cost.
Security – less security provided to the data.
So database systems became popular to overcome the above limitations of file system.
There exist few standards that are applicable to all forms of database management Systems like Relational Database Management System (RDBMS) and Object Database Management System (ODBMS). All DBMS adheres to the following two basic concepts.
ACID Properties – The acronym stands for Atomicity, Consistency, Isolation and Durability. Atomicity follows the thumb rule “All or Nothing”, while updating the data in database for the user performing the update operation. This update operation is called as transaction and it either commits (successful updating) or aborts (updating failure). Consistency ensures that the changes in data value to be constant at any given instance. This property helps in the successful transaction. Isolation property is needed during concurrent transaction. When multiple users do the transactions by accessing same object at the same time, the transaction is known as concurrent transaction. To prevent the conflict in database update, the transactions are isolated from other user and serialized. This is also known as Degree of Consistency. Durability is defined as the system’s ability to recover all committed transactions during the failure of storage or the system.
Concurrency Control and Locking – It is the DBMSs mechanism used for data sharing. When the same data is shared among multiple users, proper access control is needed and privilege of changing the applications data item is controlled through Locking.