Database Tips

What is database?

A database is a collection of related data stored in an efficient and compact manner. The word “efficient” means that stored data can be accessed very easily and quickly.

Similarly, the word “compact” means that stored data takes up as little space as possible. In the above definition of database, the phrase “related data’ is used. It means that a database contains data or information about a particular topic such as:

• Database of employees that contains data of employees of an organization or department.
  

• Database of students that contains data of students of college or university.
  

A database holds related data as well as description of that data. For this reason, a database is also defined as a self describing collection of integrated records. The description of data is known as the system catalog or data dictionary or metadata. For example when a table of a database is designed, the data type, size, format and other descriptions of fields are specified. This is an example of metadata, which describes the properties of data to be stored into fields of table.

The data of any organization is its integral part. The data is very important for developing new products and their marketing. The data must be accurate and available when needed. This is the reason that all organization must organize and manage their data into database. The databases are used for variety of purposes in as organization. For example, when you purchase goods from your local supermarket, the checkout assistant will pass the purchased product through a scanner device known as bar code reader. This device will read the bar code printed on the product and gives the accurate price of the item. Actually, the bar code reader is accessing the database, which contains the information about the products. The bar code reader is linked to a database application program, which uses the bar code to access price of item. The database program automatically updates the database. The assistant can also check whether a required item is in stock by running the database application program. Similarly, you can purchase goods using your credit card. Your credit is checked by a card reader linked to a computer system. In this case, there is a database somewhere that contains information about your credit. Almost all organizations and government departments of every country in world use database to maintain their records. Some examples of large databases that have been developed around the world are:

• When you draw amount from bank through ATM card, you are accessing the database; your account is accessed and checked through auto teller machine. When you draw some amount from your account, your record in the database is automatically updated immediately.
  

• When you visit your local library, there may be a computerized database containing details of the books in the library. There will be a computerized index, which allows you to find a book based on its title, its author’s name etc.
  

• The meteorological organization contains databases having information about current and previous meteorological data. The meteorological department is totally dependent on the meteorological data.
  

A database may be generated and maintained manually or it may be computerized. The library card catalog is an example of a database that is created and maintained manually. On the other hand, a computerized database may be created and maintained either by using application program, which is developed specifically for that purpose or by a database management systems.

Apply password and compressed feature in windows XP Tips

In windows XP, you can store your data on harddisk using less space than normal size. There is no need to install any third party software to compress or decompress your data, you can use windows built-in data compression or decompression feature to manage disk space issue.

I think many users are worried about the security of their file and folder also, so another benefit of this feature, you can protect your compressed file and folders with password.

Follow the given steps to implement the compression and password feature to mange data:

First double click on "My Computer" and locate the disk where you want to create compressed (zipped) folder. For example, if you want to create this compressed (zipped) folder on C drive, then open C drive.

Here open the "File" menu, go to "New" then click on "Compressed (zipped) Folder" option.

Rename this folder according to data information and press "Enter" button.

Now you can move (drag and drop or copy and paste) your files and folders to this compressed (zipped) folder then compression feature will implement automatically on that data.

When you want to open these compressed files, simple right click on compressed folder and click on Extract All. This extract wizard will automatically extract all these files to location you choose.

Now if you want to protect this compressed folder with password, simply open the compressed folder and go to "File" menu then here click on "Add a Password" option.

A small dialog box will appear with title "Add Password", type password in "Password" box and confirm password also then press Ok button.

Now when you will try to open your compressed files, system will prompt you a dialog box to enter password to open this file.

RAID

RAID level 0

1. Actually not use RAID redundancy does not improve in performance.
2. Data distributed on the entire disk array, is the advantage of using a large capacity disk.
3. RAID - 0 become a model of the data strip on the disk with a data management system specific to the data stored on considered a logical disk.
4. Mechanism for the transfer of data in one sector at a time so that only good for handling large data transfers.
   

RAID level 1

1. Redundancy obtained by duplicate all the data on the disk mirror.
2. As with RAID - 0, RAID - 1 stripping also use the technology.
3. The difference is in level 1 each strip mapped to the logic of the two disks that are logically separate so that each disk arrays will have a mirror disk that contains the same data.
4. RAID - 1 expensive.
5. RAID - 1 increase in performance approximately doubled compared to RAID - 0 in the operation read, but not to write operations significantly increased.
6. Matches are used to handle data that is often experienced failure in the process of reading.
7. RAID - 1 still working on sector-sector.
8. Benefits of RAID - 1:

• Request reading can be served by one of the disk because there are two disks contain the same data, depending on access to the fastest time.
• Demand for storage or writing is done on 2 disks in pararel.
• There are beack-up data, namely the disk in the mirror.
  

RAID level 2

1. RAID - 2 using the technique pararel access to all the disk. - All participating disk and executing every request so that there are mechanisms for synchronization and disk rotation head.
2. Technology used in the stripping this level, only strip small size, often in word or byte size.
3. Use a system error correction bits parity with the Hamming code.
   

RAID level 3

1. Organized similar with RAID - 2.
2. The difference in RAID - 3 requires only a single disk redudant, does not depend on the number of arrays disk.
3. Computing parity bit for each word and write data on disk pritas special.
4. When the drive failure occurs, the data re-arranged the rest of the data is still good and from information paritasnya.
5. Using pararel access to the data distributed in the form of small strip-strip.
6. Performing high-yield transfer, but can only executing a request.
7. I / O, so only if used in high data transaction environment decline in performance.
   

RAID level 4

1. Using techniques that independent access to every request so that disknya read or write served in pararel.
2. RAID is suitable to deal with the culture system data transfer rates.
3. No need synchronization because each disk operate independently.
4. Stripping the data in a large size.
5. Strip parity bits-per-bit is calculated to strip all the related data on each disk.
6. Parity stored on disk for parity.
7. When the writing operation, array management software not only to update the data but also related to parity.
8. Benefits of parity with the disk that has made special security data more secure, but with a separate disk parity will slow performance.
   

RAID level 5

1. Having a similarity with RAID - 4 in the organization.
2. The difference is strip-strip parity distributed across the entire disk.
3. For security reasons, the strip parity disk is stored on a disk other.
4. RAID - 5 improvement from the RAID - 4 in terms of improving performance.
5. Disk is usually used in the network server.
   

RAID level 6

1. It is the latest RAID technology.
2. Using the method of calculating parity for two reasons to anticipate the accuracy and error correction.
3. As with RAID - 5, parity stored on the disk other.
4. Have a high transfer speeds.

RAID Images

Mechanism Read & Write Magnetic Disk

- The process of reading and writing through Conductive coil (head).
- Head can consist of one to head out; is / read, but there are also separate.
- During the write / read, head quiet place, the move is the HD disc.
- Write
* Head moving in the magnetic disk.
* "Vibration" was sent to the head.
* A pattern (of data) written on the surface of the disk.
- Read (traditional)
* Disk rotating magnetic, adjust the "desire" head.
* The read / write head by the same.
- Read (Contemporary)
* Head divided into 2 parts to read and write.
* Operates at high speed.
> Block data more closely and more quickly.

Magnetic Disk

Magnetic Disk

• Disk is a circular disc made of certain materials (metal or plastic) surface coated with a material that can be magnetic.

• Mechanisms read / write head using read or write head is called a spindle conduction oil.

• Design physical, head are stationer disc while the disk rotates in accordance control.

• Two methods of data on the layout of diak, the constant angular velocity and multiple zoned recording.

• Disk organized in the form of ring-ring concentration called tracks.

• Each track on the disk separated by a gap (gap: prevent or reduce the reading and writing errors caused melesetnya head because of interference or magnetic fields).

• A number of bits that will occupy the same track that is available.

• As to the disk, then the density (dens Ty) disk will be large.

• Data sent to the memory of this in the form of a block, block generally smaller capacity of the track.

• Block-block data stored in the disk-sized blocks, called the sector.

• Track usually filled some sectors, generally 10 to 100 each tracknya sector.

Database Tips

What is database?

A database is a collection of related data stored in an efficient and compact manner. The word “efficient” means that stored data can be accessed very easily and quickly.

Similarly, the word “compact” means that stored data takes up as little space as possible. In the above definition of database, the phrase “related data’ is used. It means that a database contains data or information about a particular topic such as:

• Database of employees that contains data of employees of an organization or department.
• Database of students that contains data of students of college or university.
  

A database holds related data as well as description of that data. For this reason, a database is also defined as a self describing collection of integrated records. The description of data is known as the system catalog or data dictionary or metadata. For example when a table of a database is designed, the data type, size, format and other descriptions of fields are specified. This is an example of metadata, which describes the properties of data to be stored into fields of table.

The data of any organization is its integral part. The data is very important for developing new products and their marketing. The data must be accurate and available when needed. This is the reason that all organization must organize and manage their data into database. The databases are used for variety of purposes in as organization. For example, when you purchase goods from your local supermarket, the checkout assistant will pass the purchased product through a scanner device known as bar code reader. This device will read the bar code printed on the product and gives the accurate price of the item. Actually, the bar code reader is accessing the database, which contains the information about the products. The bar code reader is linked to a database application program, which uses the bar code to access price of item. The database program automatically updates the database. The assistant can also check whether a required item is in stock by running the database application program. Similarly, you can purchase goods using your credit card. Your credit is checked by a card reader linked to a computer system. In this case, there is a database somewhere that contains information about your credit. Almost all organizations and government departments of every country in world use database to maintain their records. Some examples of large databases that have been developed around the world are:

• When you draw amount from bank through ATM card, you are accessing the database; your account is accessed and checked through auto teller machine. When you draw some amount from your account, your record in the database is automatically updated immediately.
• When you visit your local library, there may be a computerized database containing details of the books in the library. There will be a computerized index, which allows you to find a book based on its title, its author’s name etc.
• The meteorological organization contains databases having information about current and previous meteorological data. The meteorological department is totally dependent on the meteorological data.
  

A database may be generated and maintained manually or it may be computerized. The library card catalog is an example of a database that is created and maintained manually. On the other hand, a computerized database may be created and maintained either by using application program, which is developed specifically for that purpose or by a database management systems.

Computer Evolution and Performance Part 11

Intel

• 1971 - 4004
• Microprocessor first
• All components of the CPU is a single chip
• 4 bits
• Following the emergence of 8008 since 1972
• 8 bits
• Microprocessor with special design application
• 1974 - 8080
• Intel is microprocessor with the general usefulness.
  

Increased speed

• Pipelining
• On board cache
• On board L1 & L2 cache
• Branch PREDICTION
• Data-flow analysis
• Speculative execution
  

Comparison of performance

• Increased processor speed.
• Increased memory capacity.
• Speed memory behind than processor speed.
  

Logic and Memory Performance Gap

Computer Evolution and Performance Part 3

IAS

• 1946, with the computer stored-program concept publised.
• Known by the name Computer IAS (Computer of the Institute for Advanced Studies).

IAS structure
Here is the structure of the computer IAS:

• Main memory, to store data and instructions.
• Arithmetic Logic Unit (pestle), for binary data.
• Control Unit, to control the instructions in memory.
• I / O, to interact with the environment outside.
  

Structure computer IAS


IAS - details

>> Memory IAS consists of 1,000 storage locations called the word.

• - Word consists of 40 bits.

• Data and Instructions in a code in binary.

• One word consists of 20 bit instructions, each - each 8 bit code operation (op code) and 12-bit address.

>> Set of Registers (storage in the CPU)

• Memory Buffer Register (MBR), contains one word, stored in memory or used to receive word from memory.

• Memory Address Register (MAR), to define the word address in memory to be written or read from the MBR by the MBR.

• Instruction Register (IR) port, 8 instruction beet contains code that the operation will be executed.

• Instruction Buffer Register (Heb), used to store instructions while the right word in memory.

• Program Counter (PC), contains the address of the next pair of instructions will be retrieved from memory.

• Accumulator (AC) and the multiplier quotient (MQ), used for temporary storage operand and the results pestle.

>> IAS operate repeatedly, forming cycle instructions.

• Computers IAS has 21 instructions, which are grouped as follows:

• Data transfer, transfer of data between memory with the register - register pestle or between two registers pestle own.

• Unconditional branch, the command - the command execution without branching certain requirements.

• Conditional branch, the execution branching certain requirements that need to produce a value of these ramification.

• Arithmetic, the operation - operations which was formed by the pestle.

• Modify Address, the instructions - instructions that allows changing the address on the so Computational address that allows high flexibility in programs.

Struktur IAS Detail


IAS Image