DBMS SHORT NOTES FOR IT OFFICERS AND GATE EXAM

Friends, in this post we shall discuss the basics of DBMS (Data Base Management Systems) which will be helpful for you for IBPS Specialist Officers Exam (IT Officers) before going into details, let’s have a look at the basic terminology of DBMS.

Data -- Data is the raw material from which Useful Information is derived.

Data (or) Information Processing -- The process of converting the facts into meaningful information is known as Data processing.It is also known as Information processing.

Meta Data -- Simply we can say it as the Data about the Data

Data Base -- A database is a collection of data (information) of some given Organization (a company for example), that can be processed through one or more programs by multiple users.

Database management systems --

DBMS are computer software applications that interact with the user, other applications, and the database itself to capture and analyze data. A general-purpose DBMS is designed to allow the definition, creation, querying, update, and administration of databases. Well-known DBMSs include MySQL, PostgreSQL, Microsoft SQL Server, Oracle, SAP and IBM DB2. A database is not generally portable across different DBMSs, but different DBMSs can inter operate by using standards such as SQL and ODBC or JDBC to allow a single application to work with more than one DBMS

Database Modal --

A database model is a type of data model that determines the logical structure of a database and fundamentally determines in which manner data can be stored, organized, and manipulated. The most popular example of a database model is the relational model (or the SQL approximation of relational), which uses a table-based format.

Common logical data models for databases include:

1. Hierarchical database model
2. Network model
3. Relational model
4. Entity–relationship model
5. Enhanced entity–relationship model
6. Object model
7. Document model
8. Entity–attribute–value model
9. Star schema

Database transaction

A transaction comprises a unit of work performed within a database management system (or similar system) against a database, and treated in a coherent and reliable way independent of other transactions. A transaction generally represents any change in database. Transactions in a database environment have two main purposes: 1. To provide reliable units of work that allow correct recovery from failures and keep a database consistent even in cases of system failure, when execution stops (completely or partially) and many operations upon a database remain uncompleted, with unclear status.
2. To provide isolation between programs accessing a database concurrently. If this isolation is not provided, the program's outcome are possibly erroneous.

A database transaction, by definition, must be atomic, consistent, isolated and durable. Database practitioners often refer to these properties of database transactions using the acronym ACID.

Atomicity

Atomicity requires that each transaction be "all or nothing": if one part of the transaction fails, the entire transaction fails, and the database state is left unchanged.

Consistency (database systems)

The consistency property ensures that any transaction will bring the database from one valid state to another. Any data written to the database must be valid according to all defined rules, including constraints, cascades, triggers, and any combination thereof.

Isolation

The isolation property ensures that the concurrent execution of transactions results in a system state that would be obtained if transactions were executed serially, i.e., one after the other. Providing isolation is the main goal of concurrency control.

Durability

Durability means that once a transaction has been committed, it will remain so, even in the event of power loss, crashes, or errors.