Saturday, July 16, 2005

Original 150 Pokemon List

Building an auditing system with "triggers" data independence

This article details the use of SQL Server 2000 diparadores in management information systems audits. Explain the two ways to perform the audit by the applications and on the boards of the database.

Monday, July 4, 2005

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Web Data Administrator

Current applications often depend on the data. In other words, the requirements of the application in question determine how to organize data in secondary storage and technology to access them. is said that an application is dependent on the data it is impossible to alter the storage structure (the physical organization of data) or access technique without affecting the application.

In a DB system is not advisable to have data-dependent applications, at least 2 reasons:

1. Each application requires a different view of the same data (eg, 2 files that work with a balance in decimal and the other in binary, the DBMS must be prepared and able to perform the conversions). Are the differences that may exist between the way you view the data for a given application and how they are physically stored.

2. The DBA should be free to modify the structure of technical storage or access (or 2 things) to adapt to changing requirements without having to modify existing applications. If your applications depend on data, such changes will certainly require corresponding changes in the programs, which would take a while for the developers could devote to creating new applications.

This independence can be defined as immunity to applications changes in the storage structure and access technique.
define 3 terms:

· A stored field is the smallest unit of stored information that is given a name. The database will include, in most cases, many occurrences (or cases) of each of the various types of stored field.

· A record stored is a set of interrelated stored fields, which has its own name. Once again the distinction between "type" and "occurrence." An occurrence of a record stored is formed by a group of occurrences of fields stored with each other (one occurrence for each different type of part).

· A file stored is the set (named) of all occurrences of a record type stored.

In systems without BD cadi always logical record of an application is identical to a corresponding stored record. This need not be so in a BD system, since the DBA may require the ability to modify the storage structure without changing the corresponding logical structures.

Friday, July 1, 2005

How Does Excersie Affect Herpes Breakout

Web Data Administrator is a web application developed by Microsoft entirely on the Net Framework for managing and running a SQL server through a Web environment.

Tuesday, June 21, 2005

Causes Tortuous Bowel

Matches Levels

CORRELATION

There are 2 levels correlation, one between the external and conceptual levels of the system and forth between conceptual and internal levels.

1. correspondence The conceptual / internal is between the concept and the database stored, specify how records and fields represent concepts at the domestic level. If you change the structure of the database stored must be modified to remain unchanged (DBA). The effects of changes should be isolated below the conceptual level, in order to preserve the independence of the data.

2. correspondence The external / conceptual is that between a given external view and the conceptual view. The differences that may exist between these 2 levels are similar to those that may exist between the conceptual and stored BD. There may be any number of external views, any number of users can share a given exterior view, there may be overlaps between different external views.

Some systems allow you to express the definition of an external view in terms of others through a correspondence external / outside instead of always needing a definition explicit correspondence regarding the conceptual level, which is useful if there is an intimate relationship between several outpatient visits. Relational systems in particular almost always allow this.

Razor Dune Buggy Local Stores

Database Administrator (DBA)

BD ADMINISTRATOR (DBA)

person who makes the policy and strategic decisions regarding company information, and the DBA is who provides technical support to implement those decisions. Therefore, the DBA is responsible for overall system control at the technical level.

DBA functions

define the conceptual schema	must decide what information should be kept in the database, ie, identify entities of interest to the company and the information to be recorded on these entities. This process is called BD logical design. The DBMS will use the version object (compiled) for that scheme to respond to requests for access. Source Version (without compiling) serve as a reference document for users of the system.
Define the internal schema	must decide how to represent information stored in the database. This process is called physical design of the database. The DBA uses the internal DDL to create the storage structure definition and the relevant correspondence between the internal and conceptual schemes (in both source and object version).
Link with users	The DBA should be responsible for communicating with users, ensuring the availability of data needed and write the required schemes. Consultations on application design, delivery technique, assistance in locating and solving problems, and other similar professional services related to the system.
Define security and integrity checks	verifications security and integrity can be considered part of the conceptual schema.
Define backup and recovery procedures	When a company decides to use a BD system, it becomes greatly dependent on proper functioning of that system . If you suffer damage any portion of the database is essential to repair the data involved with a minimum of delay and affecting as little as possible to the rest of the system. The DBA must define and implement an appropriate recovery plan that includes, for example, download, or "empty" newspaper of the BD in a backup storage media, and procedures to load the database again from casting more recently when necessary.
Monitor performance and respond to changing requirements	DBA is the responsibility of organizing the system so as to obtain better performance for the company and make appropriate adjustments when changing requirements.

How Much Does A Thong Weigh

Architecture ANSI / SPARC

THE 3 LEVELS OF ARCHITECTURE

The ANSI / SPARC architecture is divided into 3 levels called:

1. THE INTERNALLY is the closest to the physical storage. Is dealing with how data are physically stored. (DBA)

2. EXTERNAL LEVEL is the closest to the users, that is, which deals with how individual users perceive data. REPRESENTATIONS CAN MAKE AS MANY VIEWS AS USERS MAY HAVE A BD. (N. VISION)

3. CONCEPTUAL LEVEL is a mediation layer between the other two. (WORK DEFINING THE STRUCTURE OF STORAGE DBA).

There will be many "foreign views" different, each consisting of a representation more or less abstract of any part of the BD total. There will be only a "conceptual" formed by equally abstract representation of the database in its entirety.

There will be a single "inner sight" which represent all the database as stored physically.

the conceptual level will surely be relational, visible objects are relational tables (relational operators will be also.)

the external level will almost always be relational.

internal LEVEL not be "relational" because the things on that level are not usually only relational tables (stored), but are objects similar to those found in the internal level of other types of systems.

Friday, May 6, 2005

What To Use To Seal Paint

Compración

Compración between the latest stable versions of PostgreSQL and MySQL
http://monstera.man.poznan.pl/wiki/index.php/Mysql_vs_postgres

Sunday, April 17, 2005

Who Are The Host Of Smile Jamaica Tvjjamaica

PostgreSQL and Mysql Transaction Processing in Distributed Systems

Transaction

A transaction is a logical unit of work, which does not necessarily consists of a single transaction in the database, rather, is generally a sequence of such operations by which a consistent state of the database is transformed into another consistent state, without retaining by force consistency all points in between. The important point here is to ensure that the database back to a consistent state at the end of the execution of a transaction.

A transaction is also invoking a remote procedure call (RPC) running a set of operations on a database under the principle of all or nothing.

The fundamental concept here is the notion of "consistent execution? or "reliable? associated with the concept of a query. The transaction concept is used within the domain of the database as a basic unit of computing consistent and reliable.

Example 3.1: Consider the following query in SQL to implement the 10% of the project budget? CAD / CAM? of the database? J?.

J (JNO, JNOMBRE, BUDGET, LOCATION)

UPDATE J

SET BUDGET = BUDGET * 1.1

WHERE JNOMBRE =? CAD / CAM?

This query can be specified using SQL notation, as a transaction giving it a name:

Begin_transaction ACTUALIZA_PRESUPUESTO

begin

UPDATE J

SET BUDGET = BUDGET * 1.1

JNOMBRE WHERE =? CAD / CAM?

End.

Example 3.2: Consider a booking agency for airlines with the following relationships.

FLIGHT (FNO, DATE, SRC, DEST, STSOLD CAP)

CUST (CNAME, ADDR, BAL)

FC (FNO, DATE, CNAME, SPECIAL)

A simplified version of a typical reservation can be implemented by the following transaction:

Begin_transaction BOOKING

begin

input (flight_no, date, customer_name)

EXEC SQL

FLIGHT UPDATE

STSOLD SET + 1 = STSOLD

WHERE FNO = flight_no

AND DATE = date

EXEC SQL

INSERT

INTO FC (FNO, DATE, CNAME, SPECIAL)

VALUES (flight_no, date, customer_name, null)

Output (?Reservación terminada?)

End.

recovery mechanisms

In order to support a favorable response to the execution of transactions, the DBMS (System Database Manager) should handle the transaction processing. That is, should ensure that if the transaction runs some changes and then a fault (for whatever reason) before it reaches the normal end of the transaction, those changes will be void. Thus, either the transaction takes place in full, or canceled in its entirety. In this way we can persuade a sequence of operations, which in essence is not atomic, be apparent from an external point of view. The system component responsible for achieving this look is known as Manager atomicity of transactions, and COMMIT operations (committing) and ROLLBACK (back) are the key to its operation.

COMMIT operation signals the successful completion of the transaction: it tells the transaction manager that has successfully completed a logical unit of work, the database is (or should be) back in a consistent state, and that can make permanent any changes made by that unit of work.

ROLLBACK operation, however, notes and unsuccessful term of the transaction: it tells the transaction manager that something went wrong, the database could be in an inconsistent state and that all changes made so far by the logical unit of work should go back or canceled.

Example 3.3: Considering Example 3.2, consider the case when there are no seats available for booking.

Begin_transaction RESERVACION2

begin

input (flight_no, date, customer_name);

EXEC SQL

SELECT STSOLD, CAP

INTO temp1, temp2

FROM FLIGHT

WHERE FNO = flight_no

AND DATE = date

If temp1 = temp2 Then

Output (? No There are seats available?)

Abort

else

EXEC SQL

UPDATE FLIGHT

SET STSOLD = STSOLD + 1

WHERE FNO = flight_no AND DATE = date

EXEC SQL

INSERT

INTO FC (FNO, DATE, CNAME, SPECIAL)

VALUES (flight_no, date, customer_name, null)

Commit

Output (? Reservation finished?)

endif

End.

ACID (Atomicity, Consistency, Isolation, Durability)

A transaction has four basic properties

Atomicity . A transaction is an indivisible unit of work, all its actions are a Success in failure ("all or nothing").

consistency. After running a transaction must leave the state system should correct or abort. If the transaction can not reach a final state must return the system to its original state.

Isolation. The behavior of a transaction is not affected by the fact that other transactions may be running concurrently, in other words, a transaction can not reveal their results to other concurrent transactions before they commit. The transaction must serialize all accesses to shared resources and ensure that no concurrent program interfere with their respective operations.

durability. The effects of a transaction are permanent after its recording. Your changes should survive system failures. (Persistence).

LOG

ROLLBACK operation is based on the use of a? Logbook?. The DBMS (System Database Manager) maintains a daily log or on tape or disk (most commonly), which are recorded details of all update operations, in particular, initial and final values \u200b\u200bof the modified object. Therefore, if it is necessary to cancel any specific change in the system can use the entry for the blog to restore the original value of the restored object.

synchronization points

COMMIT and ROLLBACK operations establish what is called a synchronization point which represents the boundary between two consecutive transactions, or the end of a unit working logic, and therefore the point at which the base data is (or should be) in a state of consistency. The only operations that establish a sync point are COMMIT, ROLLBACK and the beginning of a program. When you set a sync point:

Commit or cancel all changes made by the program from the previous synchronization point.

all possible positioning is lost in the database.

release all records are locked.

is important to note that COMMIT and ROLLBACK end the transaction, not the program.

TYPES OF TRANSACTIONS

simple transactions. All operations are held at the same stage in a T

The transaction begins and ends with a begin_transaction either with or abort_transaction commit_transaction. The entire transaction is indivisible.

Transactions At first they were simple enough for its simplicity and its adaptation to brief bank. Currently Transactions have penetrated into all facets of the computer but have not proved more suitable, since they have a behavior

Fragile: In business transactions that extend for long periods.

Weak: In batch processing.

Null: Call to reverse.

A simple transaction takes no more than two or three seconds to avoid monopolizing critical system resources such as locks on the database. So OLTP programs are divided into short transactions executed one after another to produce results.

simple distributed transactions. A simple T can run on multiple sites and update resources located within multiple resource managers.

chained transactions (SYNCPOINT, chains and franchises). A SYNCPOINT is a point of synchronization that allows the newspaper kept the backlog within a transaction, thus allowing work to reverse the sin, abortion the transaction. However, this work is not stored permanently, so that if the system breaks down the work is lost. Chained transactions are a variation of durable SYNCPOINT to become the backlog. The sagas extend the string transactions to backtrack to a whole string if necessary.

Nested Transactions. They offer the possibility to define transactions within other transactions. each subtransaction can issue a recording or rewind to the parts assigned work.

EARLY PROTOCOL LOG

is considered that a transaction is a unit of recovery. For if a transaction is successful, the system must ensure the permanent establishment of its modifications in the database, even if the systems fall into the next moment. It is quite possible, for example, a system crash after a COMMIT made, but before the changes physically recorded in the database, you can discover the values \u200b\u200bto be recorded by examining the relevant log entries. For this, the log should have recorded physically before it can complete processing a COMMIT statement. This important rule is known as the Protocol of Early Writing Blog. Thus, the restart procedure will recover all transactions successfully completed but whose modifications failed to physically recorded before the fall.

TYPES OF FAILURES

A local fault affects only the transaction that was submitted that failure, such as a? Overflow?. Such failures are recoverable by the support mechanisms of the COMMIT statement.

A global failure affects multiple transactions (and most probably to all) of the transactions being conducted in and the moment of failure. Such failures are divided into two types:

system failures (eg electricity supply disruptions) which affect all transactions being made but not physically harm the database .

Failure of storage media (eg heads landing on the disc), which if they cause damage to the database or a portion thereof, affecting at least the transactions that are using that portion.

RECOVERY SYSTEM FAILURES

The conventional method is based on establishing a synchronous? Checkpoint?, Which implies:

physically Record content? buffers? Data on the physical database (commit the changes to the database).

Record physically track of special checkpoint in the log physically, which includes a list of all transactions being made at the time of establishment of the checkpoint.

Example:

failure was presented at the time tf.

The latest checkpoint before TF was taken at the time tv.

T1-type transactions were completed before time tv.

type T2 transactions started before and completed tv time after time and before time tv tf.

T3 type transactions were also initiated before time tv but were not completed before time tf.

T4-type transactions were initiated after the TV time and completed before time tf.

Finally, the transactions of the type T5 also started after the TV time but were not completed before time tf.

Upon restart the system must be canceled transactions types T3, T5 and must be performed again on the types of transactions T2 and T4. Note that T1-type transactions are outside the restart process, because changes are physically recorded in the database at the time tv as part of the checkpoint.

Upon reboot the following procedure is performed to identify the types of transactions T2-T5.

Start with two lists of transactions, the list and the list CANCEL REPEAT. CANCEL to match list the list of all transactions included in the checkpoint log. REPEAT leave the list empty.

Examine the log forward from checkpoint log.

If you encounter a blog entry? Initiate transaction? for transaction T, T added to the list VOID.

If you encounter a blog entry? Compromise? for transaction T, pass that transaction to the list list REPEAT CANCEL.

When you reach the end of the log, and REPEAT CANCEL lists respectively identify the transaction types T3 and T5 and the T2 and T4 types.

Then the system will check the log back, nullifying all transactions from the list VOID. Then review it forward again, again making all transactions in the Repeat list, which finalízale the recovery process.

FAILURE RECOVERY MEDIA STORAGE

A failure in the storage media is an accident in which physically destroys a portion of the database. The recovery of such failure involves essentially reload the database from a backup and then use the log (both active portion as the file in general) to make back all transactions completed since became the backup.

MONITORS TP (Transaction Processing)

A TP monitor is an operating system transaction processing that is main functions:

Process Management:

Start server processes

Channel work toward them

monitor its proper implementation

Balancing workloads

Transaction Manager

guarantees the ACID properties for all the programs under their protection

monitors specialize in managing transactions from their point of origin (usually in the client), and through one or more servers, then back to the originating client. When a T ends, the TP monitor should ensure that all systems are involved in it in a consistent state. Thus, a TP monitor know how to run T, route them between different systems, implementing load balancing and put them back on track after a crash. All this regardless of the systems, or resource managers.

arise from the need to run applications capable of serving hundreds or thousands of customers, which monitors real-time connectivity to thousands of customers who expect service without consuming many resources.

Example: If a client needs to be treated for the following resources: 1 process, 1 connection, ½ Mb of RAM and a dozen open files, and also if 1000 customers are served at the same time would have the following situations:

a). No monitor TP

1000 customers

1000 connections

1000 processes

500 MB of RAM

10000 files open

SO low performance

b). With TP monitor

1000 customers

TP MONITOR

50 connections

50 processes

25 MB RAM

500 files open

SO good performance

Usually in the PC server environments often have their applications online transaction processing (OLTP : Une On Transaction Processing) packaged as dynamic link libraries (DLL Dynamic Link Library). TP monitor, then assigns the execution of the DLL functions to server classes, background processes or threads waiting for a pre-launch work.

How does the TP monitor the act of channeling

When a client requests a service, the TP monitor even the intended process, which refers to the DLL function called by the client, invokes monitors its implementation and returns the results to the client. Once the work the server process returns the results and the process can be reused by another client. The OS keeps the DLL in memory that can be shared by other processes.

If the number of client requests received exceeds the number of server processes, the monitor dynamically start new ones (load balancing). Part of the load balancing of priorities is managing the requests received, so high priority applications are assigned to classes of high priority server. TP monitor also can divide their classes according to the type of application, desired response time, manage resources, fault tolerance requirements, etc.

A TP monitor can be seen as a client / server architecture consists of three layers: a GUI, application logic and resource managers.

BENEFITS OF A MONITOR TP

structure development of client / server. TP monitors provide a pre-built structure that helps build, operate and manage a client / server. Permits. build client / server applications robust and high performance.

protection walls. Implement protective walls between applications and resource managers, and between the same applications.

High Availability . TP monitors are designed to overcome all failures, you can create autoremediables systems, because they are always aware of the status of the resources of client / server under their control, they can detect a failure in the very moment they occur and decide if you restart the failed process or even switch back and process in another node. (Architectures without a single point of failure).

Load Balancing. TP monitors specializing in process management and technical support both static and dynamic loading; support requests with priority and can double dynamically server processes on the same or a different node.

Easy to expand functions. TP monitors encourage the creation of reusable modular procedures. The monitors only export the functions and not data, this could keep adding new features and allow the TP monitor distribute them to multiple servers. In this way one could build highly complex distributed applications by simply adding procedures.

reduced system cost. According to studies, if used TP monitors can save more than 30% of the total system cost, 40% in development costs and savings in resource acquisition.

Generally, we recommend using a TP monitor whether your client / server has more than 100 customers, which process five or more transactions per minute using three or more servers and / or uses two or more BD.

TYPES OF TRANSACTION PROCESSING

There is a qualifying transaction processing:

light (lite TP) which is limited to integrate TP monitors BD administrators.

heavy TP (TP heavy) where TP monitors extend the notion of transaction to all the resources used for processing transactions.

We can make a series of comparisons between them:

a) Scope of the recording

TP light

TP heavy

b) Resource Management. While the TP makes only slight updates to BD, the heavy TP AGIO perform updates (keeping the properties of transactions) across multiple heterogeneous resource managers within the scope of a single transaction.

c) Process Management. The light TP load the procedure, executed and if ever stored in the cache for later use. The TP heavy pre-launch feature servers, dynamic load balancing, planning according to priorities, protective walls, redirection to other servers, etc.

d) Summons client / server . TP usually has its own lightweight way to invoke the RPG server and have no authentication mechanisms, or are integrated into global directories.

e) Performance . The procedures are much faster Trligero because much reduced traffic network and require less hardware.

Source: Fernando A. http://www.ittehuacan.edu.mx/ittehuacan/
More

Thursday, April 14, 2005

Request To Disconnect Service Letter

Benefits BD's approach

Reduce redundancy

If present, must be controlled by the DBMS

In systems with BD each application has its own private files. This can cause considerable redundancy in stored data. With the consequent waste of storage space. You may have some redundancy but is controlled by the DBMS, and take responsibility for "propagating the updates."

Avoid inconsistency

(somewhat) erroneous data.

is a corollary of the above. If redundancy is eliminated, there is no inconsistency. If redundancy is not removed, there is inconsistency. Redundancy, if controlled by the DBMS ensures the consistency of the database from the point of view of ensuring user automatically apply to the other input any changes made in one of them (spread of updates). Today most of the products do not allow the controlled redundancy, except in a few exceptional cases.

Share data

DBMS is responsible if a data is being updated and the other can not access.

is possible to satisfy the information needs of new applications without having to store additional data. The chamber ( sharing ) also allows to develop new applications to work with the same stored data.

Enforce

By having centralized control of the database, the DBA (as directed by DA) may ensure compliance with all applicable standards for data representation. It is desirable primarily as support for the exchange of information or data migration between systems. The rules for naming and documenting the data is very convenient to help the chamber and comprehensibility of information.

Apply security restrictions

By having complete jurisdiction over the database, the DBA can:

a) To ensure that access the BD is only through the proper channels.

b) Define the security checks performed when attempting to access sensitive information.

verification is feasible to set different for each type of access to every piece of information from the database.

Maintaining the integrity

defines and controls the DBMS, DBA tells the DBMS

That the information is correct. To avoid erroneous information, the data administrator defines (and implements DBA) integrity checks to be made in any update operation (insertion, deletion and modification) data. Without proper controls, a user might incorrectly modify the database, creating misinformation and "infecting" and other users

Balancing conflicting requirements

By knowing the general requirements of an enterprise (as opposed to any individual user), the DBA can structure the system with a view to providing a general "best for the company." For example you may choose a form representation of the stored data with which the most important applications can have quick access while running other applications undermined.

is not so obvious but have the independence of the data (target of BD systems).

data independence :

- POSSIBILITY OF CHANGING THE STRUCTURE OF THE DATA AND NOT rewrite or CHANGE. EXAMPLE, THE LAST 20 CHARACTERS, MODIFY THE STRUCTURE OF STORAGE AND SHOULD NOT INFLUENCE IN THE PROGRAMS APPLICATION, DO NOT TOUCH.

- BUT IT IS DIFFICULT ASPIRA.

Independence may be defined as the immunity of applications to changes in the storage structure and access technique, which means that applications do not depend on a storage structure or access technique specific.

Pain Around The Navel After C.section

DATA MANAGEMENT AND ADMINISTRATION OF BD

DATA MANAGEMENT AND ADMINISTRATION OF BD

Data Administrator (DA) : Meet information and business needs in a higher management level. Their task is to decide in the first place what data should be stored in the database, and establish policies to maintain and manage the data once stored (it is a manager not a technician, although it needs to appreciate the possibilities of BD systems on a technical level .) Example security policy.

BD Manager (DBA) : A career in data processing. The task is to create the database itself and enforce technical controls needed to support policies issued by the DA. It is also responsible the proper functioning of the system and providing other related services of a technical nature. A team of several people (programmers technical assistants).

DBA	CONCEPTUAL SCHEME	- Set all storage structures and relations system of storage. - Set if file exists and with what structure.
	INTERNAL SCHEMATIC	- In what ways will the database storage and access methods or technique (eg, index).
	linked to them	- Solve problems that users may have.
	DEFINE SECURITY	- The BD system that user can use those files.
	RECOVERY AND BACK	- depends on the organization define time, size. examples disk mirrors in parallel computers, backup, etc,
	PERFORMANCE REVIEW	- Performance and go settings, displays great change form of access.

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Why use a BD? Entities and relationships

Where is multiuser there are many additional benefits, where BD is probably much larger and complex. Provides centralized control of information.

* is compact: no need for papal files that could take up much space.

* is fast, the machine can get and much faster than a human.

* is less laborious : it eliminates much of the tedium of record keeping by hand.

* is current, is available at any time of accurate and current.

has even more importance, in a multiuser environment, where the BD is probably much larger and complex than a single-user. The BD system provides the company with centralized control of information.

Different Parts Of A Pirate Ship

· Entity: means any distinguishable object to be represented in the database which we wish to record information .

· Interrelationships : they allow you to link those entities. Are represented by connecting lines or arcs. In addition, part of the information, as well as the basic entities. Are bidirectional

PROPERTIES COMPANY

are represented in the database, and are the characteristics of an entity. A given property could be very simple in nature, or possessing an internal structure of arbitrary complexity. BD current systems are not well suited to handle complex properties such as diagrams or texts.

Tuesday, April 12, 2005

How Much Is The X Games Deck

WHAT IS A SYSTEM BD? Persistent Data

WHAT IS A SYSTEM BD?

is a system for computer files, that is, is a computerized system whose purpose gral. Is to maintain information and make it available upon request.	DATA
	ARCHIVES	RECORDS	FIELDS

difference between data (values \u200b\u200bstored in the database) and information (referred to the meaning of these values \u200b\u200bfrom the point of view of a user).

RELATING TO AN ORGANIZATION, WE DETECTING PHYSICAL AND ABSTRACT COMPANIES (BANK ACCOUNT) AND YOU WILL BE RELEVANT TO THE ORGANIZATION THAT WILL BE STORED IN A PHYSICAL TO BE USED BY CERTAIN PEOPLE (INTEREST).

4 Components of a system of BD

SYSTEM BD	DATA OR INFORMATION	SHARED
		INTEGRATED
	HARDWARE OR EQUIPMENT
	SOFTWARE OR PROGRAMS	DBMS
		APPLICATION PROGRAMS
		TOOLS
	USERS

1 - INFORMATION

Multiple users can access the database at the same time, the goal is to ensure that each individual can behave as if you were working with a single user system.

should assume that all data stored in the system are kept in a single database. But in practice there may be reasons, even in small systems, to deliver information in several different databases.

The information in the database will be integrated and shared.

· Integrated : the BD can be considered as a unification of multiple data files, otherwise different, and eliminates of all or part of any redundancy between them.

· Shared: more than 1 user accesses the same data simultaneously (concurrent access or not.)

Another consequence of the fact (the integration of the database) is that usually a particular user only deal with a subset of the total database. Different users receive the database in several different ways. In fact, even when 2 users share the same subset of the database, how can see that subset significantly differ in the details.

2 - TEAM

Computers, storage, network volumes or unique to a disc.

components consisting of system equipment are

· The secondary storage volumes where stored data is preserved along with the devices I / S associated device drivers, channels of I / S, and others.

· The processor or processors and main memory associated that make possible the implementation of programs of BD.

3 - PROGRAMS

a) Among the BD physics itself and users of the system there is a level programs, the BD management system (DBMS) . The DBMS manages all requests access to the database made by the users, as well as the addition or deletion of files (tables), obtaining and updating data from those files. One of the general functions is alienate users BD details team level.

The DBMS provides users a view of the BD at a level well above the level of equipment, and makes possible its operations is an important component software but not the only (utilities, report generators, tools to develop applications).

Software consists of a set of modules, interfaces users see the data of physical media. Stored in : a data file, index files that allow faster access to stored files. By direct access pointers. And also a data dictionary containing information on the structure of data files, data type logical, Boolean, size ... (the database engine).

The DBMS is definitely the most important software component of the entire system, but not alone. among others may be mentioned the utilities, tools to develop applications for design aid, report generators, etc.

b) application programs : for a user to access data.

c) Tools : p / generate reports, forms, p / programmers and some who know a little more.

4 - USER

are taken into account three classes of users (people who interact with the system):

· Application Developer: will write application programs using the database. These programs operate on data in all the usual ways: retrieving, inserting, modifying or deleting data. It takes place appropriate requests to the DBMS. Generating applications for other users with minimal knowledge entering.

· End User: who interacts with the system from an online terminal, can access the database through an online application above, or use an interface included as an integral part of the BD system programs. (Eg SQL).

ü INGENUOUS: screen and nothing else.

ü SOPHISTICATED: data query, knows a little more, application programs.

ü SPECIALIZED: tools with images ...

Most systems also include additional integrated interfaces with which the user does not need to issue explicit commands like SELECT , but function by choosing options from a menu or a filling form. These interfaces are often easier to use for people with no formal studies of data processing. The interfaces handled by commands (such as query languages) tend to require some knowledge of data processing.

· BD Manager (DBA): Person centralizes responsibility and control of the database. Technician responsible for implementing the decisions of the Data Manager. Works together with the DA, is not considered a user, who designed the system, management position, knows the needs of the user, but is implemented by the DBA. Is a professional data processing. Your task is to create the database itself and enforce technical controls needed to support the policies dictated by the data administrator. It is also responsible for ensuring the proper functioning of the system and providing other related services of a technical nature.

orders to the system, MANAGER) DA's policy DBA (maintains contact with all users, TECHNICAL)