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.