Linggo, Hulyo 3, 2011

5  definition of DBMS


Data Security
The DBMS can prevent unauthorized users from viewing or updating the database. Using passwords, users are allowed access to the entire database or a subset of it known as a "subschema." For example, in an employee database, some users may be able to view salaries while others may view only work history and medical data.

Data Integrity
The DBMS can ensure that no more than one user can update the same record at the same time. It can keep duplicate records out of the database; for example, no two customers with the same customer number can be entered.

Interactive Query
A DBMS provides a query language and report writer that lets users interactively interrogate the database. These essential components give users access to all management information as needed. See query language and report writer.

Interactive Data Entry and Updating
A DBMS typically provides a way to interactively enter and edit data, allowing you to manage your own files and databases. However, interactive operation does not leave an audit trail and does not provide the controls necessary in a large organization. These controls must be programmed into the data entry and update programs of the application.

This is a common misconception about using a desktop computer DBMS. Creating lists of data for a user's own record keeping is one thing. However, although complete information systems can be developed with such software, it cannot be done without understanding how transactions and files relate to each other in a business system (see Database Design below). In addition, some type of programming is required, whether at a graphical drag and drop level or by using traditional languages.

Data Independence
When a DBMS is used, the details of the data structure are not stated in each application program. The program asks the DBMS for data by field name; for example, a coded equivalent of "give me customer name and balance due" would be sent to the DBMS. Without a DBMS, the programmer must reserve space for the full structure of the record in the program. Any change in data structure requires changing all application programs.




Top 5 Data  definition

            

               Data is a collection of distinct pieces of information, particularly information that has been formatted (i.e., organized) in some specific way for use in analysis or making decisions.

  • NYSE Launches Cloud Platform for Traders – NYSE Euronext today entered the cloud computing business, launching a platform that allows financial traders to lease computing power at the NYSE’s new data center in northern New Jersey. The new platform, operated by NYSE Technologies, was developed with technology from VMware and EMC.
  • Apple Confirms the Approach of the iCloud – Apple today confirmed that it will announce details for “iCloud, Apple’s upcoming cloud services offering,” at the company’s annual Worldwide Developers Conference next Monday. The announcement confirms the long-held assumption that the size of Apple’s new data center in North Carolina was a sure sign of a coming cloud offering.
  • Power Usage Effectiveness 2 – The Sequel – On May 17th the Data Center Efficiency Task Force issued a 14 page document entitled “Recommendations for Measuring and Reporting Version 2 – Measuring PUE for Data Centers” – also known as PUE 2. The updated PUE version is meant to clarify and reiterate the updated measurement requirements of the PUE metric and presumably prevent “PUE envy.”
  • Bid to Extend Washington State Tax Break Fails – A bill in Washington state that would have extended a key sales tax exemption for data center construction has died, meaning the tax break will expire at the end of this month. The bill passed the Senate 41-1 and moved out of the House Ways Committee via a unanimous vote, but never came up for a vote in the House.
  • Tornado Risk Seen for Social Security Project – The Social Security Administration has elected to build its new $800 million data center to withstand wind speeds of only 90 miles an hour, rather than the 120 miles an hour standard common in most mission critical facilities.
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Biyernes, Hulyo 1, 2011

top 5 definition of database

 

Top 5 Best Databases

A database is a set of data that has a regular structure and that is organized in such a way that a computer can easily find the desired information.

As part of the contest we conducted recently, we got 160+ comments from the geeky readers who choose their favorite database.
Based on this data, the top spot goes to.. drum roll please..
MySQL
If you are new to any of the top 5 database mentioned here, please read the rest of the article to understand more about them.


1. MySQL


MySQL is used in almost all the open source web projects that require a database in the back-end. MySQL is part of the powerful LAMP stack along with Linux, Apache and PHP.
This was originally created by a company called MySQL AB, which was acquired by Sun Microsystems, which was acquired by Oracle. Since we don’t what Oracle will do with MySQL database, open source community has created several forks of MySQL including Drizzle and MariaDB.




Following are few key features:
  • Written in C and C++.
  • MyISAM storage uses b-tree disk tables with index compression for high performance.
  • Support for partitioning and replication.
  • Support for Xpath, full text search.
  • Support for stored procedures, triggers, views etc.,
Additional Information:

2. PostgreSQL

PotgreSQL is a open source object-relational database system. It runs on most *nix flavours, Windows and Mac OS. This has full support for joins, views, triggers, stored procedures etc.,
Following are few key features:
  • MVCC – Multi-Version Concurrency Control
  • Hot backups and point-in-time recovery
  • Support for tablespaces
  • Asynchronous replication
  • Highly scalable
Additional Information:

3. Oracle

Oracle is the best database for any mission critical commercial application. Oracle has following four different editions of the database: 1) Enterprise Edition 2) Standard Edition 3) Standard Edition One 4) Express Edition
Following are few key features of the oracle database.
  • Real Application Cluster (RAC)
  • Data Guard for standby database
  • Virtual Private Database
  • Automatic Memory, Storage and Undo Management
  • OLAP, Partitioning, Data Mining
  • Advance Queuing, XML DB, Support for Spatial data
  • Flashback Database, Query, Table and Transaction
Additional Information:

4. SQLite

SQLite does not work like a traditional client-server model with standalone process. Instead, it is a self-contained, server-less SQL database engine.
Main Features of SQLite:
  • Zero configuration with no setup or admin tasks.
  • Complete database is stored in a single disk file.
  • No external dependencies
  • Supports database of several TB in size
  • Work on most *nix flavors, Mac OS X, windows. It’s also cross-platform.
  • WinCE is supported out-of-the box
Additional Information:

5. Microsoft SQL Server

This is Microsoft’s flagship Database product. If you are stuck in a company that heavily uses Microsoft products, you might end-up working on MS SQL Server.
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Sabado, Hunyo 25, 2011

flat file db models & physical electronics




Network model Vs. Flat file db model


The Difference between Network and Flat file model


  The network model is adatabase model conceived as a flexible way of representing objects and their relationships. Its distinguishing feature is that the schema, viewed as a graph in which object types are nodes and relationship types are arcs, is not restricted to being a hierarchy or lattice.







Vs.
A flat file database describes any of various means to encode a database model (most commonly a table) as a single file (such as .txt or .ini).

Hierarchical model vs. Flatfile db model



 The Difference between Hierarchical and Flat file model


A hierarchical data model is adata model in which the data is organized into a tree-like structure. The structure allows representing information using parent/child relationships: each parent can have many children but each child only has one parent (also known as a 1:many ratio ). All attributes of a specific record are listed under an entity type.



Vs.

 



A flat file database describes any of various means to encode adatabase model (most commonly atable) as a single file (such as .txtor .ini).


relational model Vs flat file db model

A flat file database is a database designed around a single table. The flat file design puts all database information in one table, or list, with fields to represent all parameters. A flat file may contain many fields, often, with duplicate data that are prone to data corruption. If you decide to merge data between two flat files, you need to copy and paste relevant information from one file to the other. There is no automation between flat files. If you have two or more flat files that contain client addresses, for example, and a client moved, you would have to manually modify the address parameters in each file that contains that client’s information. Changing information in one file has no bearing on other files. Flat files offer the functionality to store information, manipulate fields, print or display formatted information and exchange information with others, through email and over the Internet. Some flat files may be attached to external files, such as text editors, to extend functionality and manage related information.

Relational Database

A relational database, on the other hand, incorporates multiple tables with methods for the tables to work together. The relationships between table data can be collated, merged and displayed in database forms. Most relational databases offer functionality to share data:
  • Across networks
  • Over the Internet
  • With laptops and other electronic devices, such as palm pilots
  • With other software systems

Object model Vs Flat File db model

An object database (also object-oriented database management system) is adatabase management system in which information is represented in the form of objectsas used in object-oriented programming. Object databases are a niche field within the broader database management system (DBMS) market dominated by relational database management systems. Object databases have been considered since the early 1980s and 1990s, but they have made little impact on mainstream commercial data processing, though there is some usage in specialized areas.A "flat file" is a plain text or mixed text and binary file which usually contains one record per line[2] or 'physical' record (example on disc or tape). Within such a record, the single fields can be separated by delimiters, e.g. commas, or have a fixed length. In the latter case, padding may be needed to achieve this length. Extra formatting may be needed to avoid delimiter collision. There are no structural relationships between the records.
Typical examples of flat files are /etc/passwd and /etc/group on Unix-like operating systems. Another example of a flat file is a name-and-address list with the fields Name,Address, and Phone Number.
A list of names, addresses, and phone numbers written on a sheet of paper is a flat file database. This can also be done with any typewriter or word processor. A spreadsheet ortext editor program may be used to implement flat file databases.


Multi-dimensional model VS Flat file database

Multi-dimensional model is an integral aspect of the On-line Analytical Processing which also known as OLAP.While the Flat file database is a database designed around a single table. The flat file design puts all database information in one table, or list, with fields to represent all parameters. A flat file may contain many fields, often, with duplicate data that are prone to data corruption. If you decide to merge data between two flat files, you need to copy and paste relevant information from one file to the other. There is no automation between flat files. If you have two or more flat files that contain client addresses, for example, and a client moved, you would have to manually modify the address parameters in each file that contains that client’s information. Changing information in one file has no bearing on other files. Flat files offer the functionality to store information, manipulate fields, print or display formatted information and exchange information with others, through email and over the Internet. Some flat files may be attached to external files, such as text editors, to extend functionality and manage related information.

  • Physical Electronics

The Physical Electronics group focuses on theoretical and experimental research projects involving fabrication of electronic materials and new and advanced devices as well as organic and inorganic micro/nanostructures for device applications. A major focus is creating technologies that enable new levels of performance in devices, circuits, systems, sensors and energy conversion/harvesting. The UC Davis Nanofabrication Facility (known as Northern California Nanofabrication Center), with over 13,000 square feet of class-100 cleanroom, is the largest modern teaching and research facility of its kind in the U.S for micro and nano devices, biotechnological fabrication and integration. In addition, there is a Materials Science Central Facility and Advanced Characterization Lab to facilitate the research activities in this field.
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