ORACLE DATABASE RECOVERY

There are several circumstances that can halt the operation
of an Oracle database. The most common are :


User errors - User errors whether data entry or alterations causing
invalid or incorrect data, can require a database to be recovered to
a point in time before the error occurred.

For example, a user might accidentally drop a table, causing the database
to need to be restored to a point in time just before this happened.




Instance failure - This occurs when a problem arises which prevents
an instance (SGA and background process) from continuing work.
This is usually due to a power failure, a SHUTDOWN ABORT statement,
a STARTUP FORCE statement, or possibly an operating system crash.
When this happen, data that is stored in the SGA buffers is not written
to disc. This type of failure requires instance recovery and is done
automatically by Oracle at instance startup by applying Redo logs to
recover the committed data in the SGA.


Media failure - This occurs anytime there is a failure to read or write
data to disc. This is usually caused by a disc head crash which causes
loss of some or all files on the drive. Different Oracle files
(Data, Control, Redo) may be affected and the particular file type may
require different types of recovery. Also, since the instance cannot
execute properly, data in it's buffers is not written to disc.
This type of failure requires media recovery which entails restoring
backup files so that information in them corresponds to the most recent
time prior to the disk failure including committed data in memory.


Statement errors - These errors are usually caused by improperly encoded
SQL statements and their effects on data are typically undone by oracle
before control is returned to the user.


Process failure - This occurs when a process aborts prematurely. The
oracle process PMON detects this halt and rolls back the uncommitted
transactions before releasing resources held by that process.

System Data Recovery

The final goal of the Data Recovery process is to ensure
that all committed transactions prior to the database failure
are fully recovered and are reflected once the instance
is re-started.

To initiate a data base recovery,some pre-recovery steps
should be completed

1. Identifying the type of error and determining a fast and
effective action to take. Most common errors are:

- User
- Process
- Instance
- Media

2. Risk Measure : identifying the risks associated with the
database failure ( Business data loss )

3. Identification of Data Recovery Mode

Primary Key : Concept

A relational database is based on the concept that the user that
queries the database needs not remember the physical location of
the record that he/she needs access to.

the user only needs to remember the table name and
the value that the user associates to.

that's why a relational database must contain a unique identifier
for each record that exists in the relational database.

thus the concept of primary key arises that provides a unique
identifier for each record called as the "PRIMARY KEY".

ORACLE Logical Database Structures

Tablespaces

A database is divided into logical storage units called
tablespaces,which group related logical structures together.
One or more datafiles are explicitly created for each tablespace
to physically store the data of all logical structures in a
tablespace.

Oracle Data Blocks

Oracle database data is stored in data blocks. One
data block corresponds to a specific number of bytes of
physical database space on disk.
The standard block size is specified by the DB_BLOCK_SIZE
initialization parameter.

Extents

An extent is a specific number
of contiguous data blocks, obtained in a single allocation,
used to store a specific type of information.

Segments

A segment is a set of extents allocated for a certain logical
structure.

Types Of Segments -

Data segment
Index segment
Temporary segment
Rollback segment

ORACLE Physical Database Structures

Datafiles

Every Oracle database has one or more physical datafiles.
The datafiles contain all the database data.
The data of logical database structures, such as tables and
indexes, is physically stored in the datafiles allocated for a
database.

Control Files

Every Oracle database has a control file. A control file contains
entries that specify the physical structure of the database.
For example, it contains the following information:


Database name

Names and locations of datafiles and redo log files

Time stamp of database creation


Redo Log Files

Every Oracle database has a set of two or more redo log files.
The set of redo log files is collectively known as the redo log
for the database. A redo log is made up of redo entries (also called
redo records).
The primary function of the redo log is to record all changes made
to data. If a failure prevents modified data from being permanently
written to the datafiles, then the changes can be obtained from the
redo log, so work is never lost.

Archive Log Files

You can enable automatic archiving of the redo log. Oracle
automatically archives log files when the database is in ARCHIVELOG mode.

Parameter Files

Parameter files contain a list of configuration parameters for
that instance and database.

Oracle Application Development Feature Improvements

Application Program Interface (API) and precompilers


Oracle provides Open Database Connectivity (ODBC) Driver Support for Linux.

Now you can develop ODBC applications on Linux platforms.


Oracle Call Interface (OCI) Client Version API - This allows applications to be compiled for multiple versions of the Oracle client from a single source code environment.


Start Up and Shut Down of Database OCI API –

This feature adds API calls for starting and stopping a database from inside an application. This enables testers to start up and shut down databases without using SQL*Plus or other tools.

Globalization and Unicode Improvements

Oracle's Unicode character sets, AL32UTF8 and AL16UTF16, have been updated to support Unicode 4.0 in Oracle Database 10g Release 2.

Globalization Development Kit (GDK) 2.0 -

Globalization Development Kit (GDK) has added new locales and common locale mapping information into the GDK for the PL/SQL package.

Oracle GRID Computing

For years, when you needed more computing capacity, you bought more expensive computers. Now, with the Oracle Grid, add capacity on demand with one inexpensive PC server at a time for superior scalability and fast ROI. And if one department needs more capacity, use Oracle software to borrow it from another while the grid just keeps running. The Oracle Grid. Runs faster. Costs less. And never break

Grid Benifits

• Flexibility to meet changing business needs
• High quality of service at low cost
• Faster computing for better information
• Investment protection and rapid ROI


Oracle Grid Computing: Standardization

Every business today has a mix of server and storage technologies. By standardizing these technologies, you can significantly lower costs and in the process form the basis of a grid computing infrastructure. Here are some of the grid computing technologies that will drive down the cost of your infrastructure:
Low-cost, high volume Intel or AMD processors provide the benefits of proprietary processors at a fraction of the cost
Blade server technology reduces the cost of hardware and increases the density of servers

Network storage technologies such as Network Attached Storage (NAS) and Storage Area Networks (SANs) further reduce disk storage costs
Gigabit Ethernet and Fibre Channel drives down the cost of connecting clusters of servers

Linux provides a cost-effective and enterprise-ready operating system
Once you've standardized on low-cost servers and storage, consolidate your databases, application servers and storage, and automate day-to-day management tasks.

Oracle Grid Computing: Consolidate

Another step toward grid computing is to consolidate your infrastructure using clusters of servers. Oracle 10g is the only infrastructure that has full grid server cluster capabilities for all applications–transaction processing (OLTP), decision support (DSS), and enterprise content management. With Oracle Application Server clusters and with the Oracle Real Application Clusters option for the Oracle Database you can increase reliability and reduce management costs by as much as 20%. And only Oracle can run your existing applications in a grid computing environment with no rewrite required.

Oracle Grid Computing: Automate

Automate your grid so you can manage it effectively as it grows. Because enterprise grids can have hundreds, potentially thousands of servers, a grid is simply too large to be managed manually server-by-server. Oracle Enterprise Manager 10g has automated the day-to-day maintenance required for an enterprise grid, and provides a centralized management console called Oracle Grid Control.
Software installation, patching, upgrading, workload balancing, security, and much more are all handled centrally from Oracle Grid Control. This means the entire infrastructure can be managed as one large computing system. One or a few administrators can maintain even the largest grid data center.

Oracle 10g New Features

RECOVERABILITY/SECURITY

Flashback


Flashback Database
Flashes back changes to entire database

- Powerful feature to help in resolution of user errors that cause
changes to database

- Much faster method of recovering data than other methods
(tablespace point in time recovery, logical backups, or log miner)


Flashback Drop
-Allow you to undo the effects of a drop table

-Concept of a recycle bin

Flashback Versions Query
-Allows you to see all versions of data for a given row over a period of time



Flashback Transaction

-Reconstructs the SQL statements that have been previously executed in the database

ENTERPRISE GRIDS WITH REAL APPLICATION CLUSTERS

Real Application Clusters (RAC) enables the enterprise to build database servers across multiple systems that are highly available and highly scalable. In a Real Application Clusters environment Oracle runs on two or more systems in a cluster while concurrently accessing a single shared database. What this provides is a single database system that spans multiple hardware systems yet appears to the application as a single unified database system. This extends tremendous availability and scalability benefits for all your applications.

Real Application Clusters enables enterprise Grids. Enterprise Grids are built out of large configurations of standardized, commodity-priced components: processors, servers, network, and storage. RAC is the only technology that can harness these components into useful processing system for the enterprise. Real Application Clusters and the Grid dramatically reduce operational costs and provide new levels of flexibility so that systems become more adaptive, proactive, and agile. Dynamic provisioning of nodes, storage, CPUs, and memory allow service levels to be easily and efficiently maintained while lowering cost still further through improved utilization. In addition, Real Application Clusters is completely transparent to the application accessing the RAC database and does not need to be modified in any way to be deployed on a RAC system.

Real Application Clusters gives users the flexibility to add nodes to the cluster as the demands for capacity increases, scaling the system up incrementally to save costs and eliminating the need to replace smaller single node systems with larger ones. Grid pools of standard low cost computers and modular disk arrays make this solution even more powerful with the Oracle Database 10g.

Oracle 10g Features

High Availability

Enterprises have used their information technology (IT) infrastructure to provide competitive advantage, increase productivity, and empower users to make faster and more informed decisions. However, with these benefits has come an increasing dependence on that infrastructure. Should a critical application, server or data become unavailable, the entire business can be placed in jeopardy. Revenue and customers can be lost, penalties can be owed, and bad press can have a lasting effect on customers and a company's reputation. Building a high availability IT infrastructure is critical to the success and well being of all enterprises in today's fast moving economy.

Grid computing is a new computing architecture that effectively pools large numbers of servers and storage into a flexible, on-demand computing resource for all enterprise computing needs. Technology innovations like low-cost blade servers, small and inexpensive multiprocessor servers, modular storage technologies, and open source operating systems like Linux provide the raw material for the Grid. By harnessing these technologies, and leveraging the Grid technology available in the Oracle Database 10g, enterprises can deliver extremely high quality of service to their users while vastly reducing their expenditures on IT.

Holographic STORAGE

Holographic storage is computer storage that uses laser beams to store computer-generated data in three dimensions.

Storing information throughout the volume of a medium—not just on its surface—offers an intriguing high-capacity alternative. Holographic data storage is a volumetric approach which, although conceived decades ago, has made recent progress toward practicality with the appearance of lower-cost enabling technologies, significant results from longstanding research efforts, and progress in holographic recording materials.

In holographic data storage, an entire page of information is stored at once as an optical interference pattern within a thick, photosensitive optical material.

In addition to high storage density, holographic data storage promises fast access times, because the laser beams can be moved rapidly without inertia, unlike the actuators in disk drives. With the inherent parallelism of its pagewise storage and retrieval, a very large compound data rate can be reached by having a large number of relatively slow, and therefore low-cost, parallel channels.

Wireless Charging

Imagine a world where all your portable devices can be charged and powered simply by placing them on a desktop. Chip manufacturer MobileWise has gone well beyond imagining such a world and this week unveiled "a conductive solution" that it believes can make it all possible.

The patent-pending technology behind the MobileWise is, on the surface, quite simple. The adapter chip inside the handheld device will, when placed on a base station, receive a very small electrical signal and message from the base controller chip that will power up the adapter chip. The base controller chip will sense for polarity. If there is none (say you place your hand on the base) then it does nothing. If it does find polarity and then a signal from the adapter chip, it will then read information about the voltage level necessary to run the mobile device and begin charging and powering it.

EXTREME TECH: Wearable CAR

Awsome is the only word that your mouth utters when you experiance it.

HOW the power of technology is realised in to human convenience is exemplified
with TOYOTA iSwing Concept CAR.

This is a concept car designed by Hideo Miwa from Toyota. It's named the i-swing and looks like a chair on wheels.This is a new breed of wearable robotic vehicles that envelop drivers.

you can have a visual experiance of the tech at

Web Services

According to World Wide Web Consortium

A Web service is a software system designed to support interoperable machine-to-machine
interaction over a network. It has an interface described in a machine-processable format (specifically WSDL).

Other systems interact with the Web service in a manner prescribed by its description using
SOAP messages, typically conveyed using HTTP with an XML serialization in conjunction with other Web-related standards.



Web services provide a standard means of interoperating between different software applications, running on a variety of platforms and/or frameworks.

WEB 2.0 Experiance

Web 2.0 - Page Flakes


Pageflakes is your personalized startpage on the Internet. Your address book, local weather information, to-do-list, news, blogs and much more – all on one page that you can access from anywhere.

you can experiance the power of web 2.0 easily,
Signup PageFlakes at:
http://www.pageflakes.com/?source=d0717228-af8a-4514-b1bb-2f187db03bc7


Why should we use Pageflakes?

Until now you had to go to different web sites to check your email, start Web searches, get weather information and so on. With Pageflakes, everything you need is on one page! You can also use Pageflakes to keep up with your favorite blogs and news feeds. And best of all, it's free!

Most flakes can be customized to your personal preferences. For example, you can enter your ZIP code in Weather Flake to get the local weather forecast for your area, and you can enter a category like "sports" in YouTube Video Flake to get videos from that category. To choose your settings, just click on the little "EDIT" link at the top right of the flake.

DATA WAREHOUSING CONCEPTS

characterization of data warehouses

a datawarehouse is

1) Subject-oriented, meaning that the data in the database is
organized so that all the data elements relating to the same
real-world event or object are linked together.

2) Time-variant, meaning that the changes to the data in the
database are tracked and recorded so that reports can be
produced showing changes over time.

3) Non-volatile, meaning that data in the database is never
over-written or deleted, but retained for future reporting.

4) Integrated, meaning that the database contains data from
most or all of an organization's operational applications, and
that this data is made consistent.

SUN DEVELOPERS CONFERENCE IN INDIA

Sun Tech Days

Your opportunities are wide open at Tech Days, Sun's Worldwide Developer Conference!Coming Soon to india:


Hyderabad, India: February 21-23, 2007

HOW to BUILD a Data Warehouse ?

Bluetooth - an introduction

First Vision