“THE DATABASE AND DATABASE MANAGEMENT SYSTEM”

Mossawir AhmedBB-1666

DATA MANAGEMENTData management is the development and execution of architectures, policies, practices and procedures in order to manage the information lifecycle needs of an enterprise in an effective manner.

DATA MANAGEMENT ACTIVITIES

The data management activities include

• DATA COLLECTION• INTEGRITY & VERIFICATION• STORAGE• MAINTENANCE• SECURITY• ORGANIZATION• RETRIEVAL

All Computers include some type of secondary storage to supplement the primary storage that is housed in the CPU. The two main types of secondary storage are sequential and direct access.

SECONDARY STORAGE

SEQUENTIAL STORAGESequential storage is an organization or arrangement of data on a storage medium that consists of one record following another in a particular order

MAGNETIC TAPE STORAGE

A device for storing information, in which signals are recorded by lining up small bits of magnetic materials in the coating on the tape.

MAGNETIC TAPE RECORD

A mechanical device for recording on magnetic tape and usually for playing back the recorded material

DIRECT ACCESS STORAGEA type of storage device, such as a magnetic disk, in which bits of data are stored at precise locations, enabling the computer to retrieve information directly without having to scan a series of records

MAGNETIC DISK STORAGE

The disks that are used to record computer data are usually made of metal and are covered with the same recording material that is used on magnetic tape.

READING & WRITING DISK DATA

When data is to be read from or written to a disk, it is first necessary to position the access mechanism on the proper track and then activate the proper read/write head.

RECORD ADDRESSING

There are three basic approaches to producing the address that the DASD requires to access a record. The approaches are direct addressingdirect addressing, hashinghashing, and indexed sequentialindexed sequential

Umair AhmedBB-1629

THE RELATIONSHIP OF SECONDARY STORAGE PROCESSINGThere are two principal ways to process data batch processing and online processing. Batch Processing involves holding transactions and processing them all at once, in batches. Online processing involves processing the transaction individually, often at the time they occur, because online processing is transaction processing oriented, the term transaction processing is often used.

BATCH PROCESSING

Batch processing is execution of a series of programs ("jobs") on a computer without manual intervention.

ONLINE PROCESSING

ONLINE PROCESSING

Online transaction processing, or OLTP, refers to a class of systems that facilitate and manage transaction-oriented applications, typically for data entry and retrieval transaction processing.

THE DATABASE CONCEPTA database is an integrated collection of logically related records or files consolidated into a common pool that provides data for one or more multiple uses. This logical integration of recordsin multiple files is called the database concept.Two primary goals of the database concept are tominimize data redundancy and to achieve data independence.

DATA REDUNDANCY

Writing data to two or more locations for backup and data recovery. For example, data can be stored on two or more disks or disk and tape or disk and the Internet.

DATA INDEPENDENCE

Data independence is the type of data transparency that matters for a centralized DBMS. It refers to the immunity of user applications to make changes in the definition and organization of data.

S.M.WAQARBB-1740

A MODEL OF A DBMSA model that shows the major DBMS elements is pictured. The elements include a data description language processor, a performance statistics processor, a backup/ recovery module,and a database manager.

DATA DESCRIPTION LANGUAGE PROCESS

The data description language processor transforms the data dictionary into the database schema.This is the DDL described earlier. All DBMSs have a DDL.

PERFORMANCE STATISTICS PROCESSOR

The performance statistics processor maintains statistics that identify what data is being used, who is using it, when it is being used, and so forth. The statistics are used in managing the database. Microcomputer-based DBMSs typically do not include elements.

BACKUP/RECOVERY MODEL

Periodically, such as daily, a backup copy of the database is made, As subsequent transactions are processed against the master files, a transaction log keeps a record of all changes.

DATABASE MANAGER

The database manager is the most important element insofar as it handles the user’s data requests.

DATABASE ADMINISTRATORAn information specialist who has responsibility for the database is called a database administrator (DBA). The duties of the DBA fall into four major areas: planning, implementation,operation, and security.

DATABASE PLANNING

Database planning involves working with managers to define the firm’s schema, and with users to define their subschemas

DATABSE IMPLEMENTATION

Database implementations consist of creating the database to conform to the specifications of theselected DBMS, as well as establishing and enforcing policies and procedures for database use

DATABASE OPERATION

Database operation includes offering educational programs to database users and providing assistance when needed.

DATABASE SECURITY

Database security is the system, processes, and procedures that protect a database from unintended activity

NIDA SARWARBB-1614

PUTTING THE DATABASE AND DBMS IN PRESPECTIVEThe DBMS makes it possible to create a database in the computer’s direct access strong, maintain its contents, and make the contents available to users without costly custom programming.When firms or individual users decide whether to use a DBMS, they must weightthe advantage and the disadvantage.

DBMS ADVANTAGESThe DBMS enables both firms and individual users to:

1. REDUCE DATA REDUNDANCY

The total number of files is reduced by deleting duplicate files. There is also a minimum of common data among files.

2. INTEGRATE DATA FROM MULTIPLE FILES

When the files are constructed so as to provide logical linkages, the physical organization no longer is a constraint.

3. IMPROVE SECURITY

Both mainframe computer and microcomputer DBMSs can include multiple levels of securityprecautions such as passwords, user directories, and encryption

DBMS DISADANTAGES

1. OBTAIN EXPENSIVE SOFTWARE

The mainframe DBMSs remain very expensive. The microcomputer-based DBMSs, while costing only a few hundred dollars, can represent a substantial outlay for a small Organization.

2. OBTAIN LARGE HARDWARE CONFIGURATION

The DBMSs often require large primary and secondary storage capacities than are required by the application program.

3. HIRE & MAINTAIN A DBA STAFF

The DBMS requires specialized knowledge in order to make full use of its capabilities. This specialized knowledge is best provided by DBAs.

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