Skip to main content

various characteristics of DBMS approach

1. Self-contained nature
      DBMS system contains data plus a full description of the data (called “metadata”) “metadata” is data about data - data formats, record structures, locations, how to access, indexes metadata is stored in a catalog and is used by DBMS software to know how to access the data. Contrast this with the file processing approach where application programs need to know the structure and format of records and data.
2. Program-data independence
      Data independence is immunity of application programs to changes in storage structures and access techniques. E.g. adding a new field, changing index structure, changing data format, In a DBMS environment these changes are reflected in the catalog. Applications aren’t affected. Traditional file processing programs would all have to
change, possibly substantially.
3. Data abstraction
      A DBMS provides users with a conceptual representation of data (for example, as objects with properties and inter-relationships). Storage details are hidden. Conceptual representation is provided in terms of a data model.
4. Support for multiple views
      DBMS may allow different users to see different “views” of the DB, according to the perspective each one requires. E.g. a subset of the data - For example; the people using the payroll system need not/should not see data about students and class schedules. E.g. data presented in a different form from the way it is stored - For example someone interested in student transcripts might get a view which is formed by combining information from separate files or tables.
5. Centralized control of the data resource
      The DBMS provides centralized control of data in an organization.
      This brings a number of advantages:
      (a) reduces redundancy
      (b) avoids inconsistencies
      (c) data can be shared
      (d) standards can be enforced
      (e) security restrictions can be applied
      (f) integrity can be maintained
a, b. Redundancy and Inconsistencies
      Redundancy is unnecessary duplication of data. For example if accounts department and registration department both keep student name, number and address.
      Redundancy wastes space and duplicates effort in maintaining the data.
      Redundancy also leads to inconsistency.
      Inconsistent data is data which contradicts itself - e.g. two different addresses for a given student number. Inconsistency cannot occur if data is represented by a single entry (i.e. if there is no redundancy).
      Controlled redundancy: Some redundancy may be desirable (for efficiency). A DBMS should be aware of it, and take care of propagating updates to all copies of a data item.
      This is an objective, not yet currently supported.
c. Sharing
      • Need concurrency control
      • Multiple user views
d. Standards
      E.g. data formats, record structures, naming, documentation
      International,   organizational, departmental ... standards
e. Security
      - restricting unauthorized access
      DBMS should perform security checks on all accesses.
f. Integrity
      Maintaining validity of data;
      e.g. employee numbers must be in some range
      e.g. every course must have an instructor
      e.g.. student number must be unique
      e.g. hours worked cannot be more than 150
      These things are expressed as constraints.
      DBMS should perform integrity checks on all updates. Currently DBMSs provide limited integrity checks.
 

Comments

  1. Anonymous8 April 2013 at 01:05

    How do u identify entities

    ReplyDelete
  2. Anonymous13 April 2013 at 18:02

    Dont let the packaging fool you into buying something that may damage your hair.
    Comb the excess oil through the dampened hair, making
    sure to cover the ends of the hair. You repeat the exact same procedure maybe once or twice every
    week. The remaining oil in the scalp for a day and then follow
    up with a shampoo the next morning. Goodness of traditional herbs work wonders
    for colored, straightened and chemically treated hair.


    Here is my blog post - hair straighteners

    ReplyDelete
  3. Anonymous21 April 2013 at 09:36

    Djelloul: The Mafia has been portrayed in many ways in books and movies, and I don't have a quarrel with these portrayals, because the Mafia is a work of many facets. This is a growing and profitable market with the increase in ability for all types of business- large or small - to do business in an international platform and other is National Newspaper Networks combine newspapers from several States within the USA. They also tend to endear themselves to populations in times of severe duress and hardship by well funded relief efforts and other charitable initiatives, which make them look incredibly social compared to corrupted governments. He proudly displays a disdain for homosexuals, especially those that are HIV-positive, by stating that they should be sequestered away from the rest of Frances moral society. A Christian newspaperis also associated with various charitable institutions and churches and organizes fund raising events to help and aid such institutions.

    Feel free to surf to my web-site ... click here

    ReplyDelete

Post a Comment

Popular posts from this blog

Pointers in C

Pointers are an extremely powerful programming tool. They can make some things much easier, help improve your program's efficiency, and even allow you to handle unlimited amounts of data. For example, using pointers is one way to have a function modify a variable passed to it. It is also possible to use pointers to dynamically allocate memory, which means that you can write programs that can handle nearly unlimited amounts of data on the fly--you don't need to know, when you write the program, how much memory you need. Wow, that's kind of cool. Actually, it's very cool, as we'll see in some of the next tutorials. For now, let's just get a basic handle on what pointers are and how you use them. What are pointers? Why should you care? Pointers are aptly name: they "point" to locations in memory. Think of a row of safety deposit boxes of various sizes at a local bank. Each safety deposit box will have a number associated with it so that you ca...
30 comments
Read more

Types of Computer Networks(LAN,MAN,WAN)

Types of Computer Networks Computer networks are categorized according to: How they are organized physically. The way they are used. The distance over which they operate. Three main types of computer networks are as follows: LAN   (Local Area Network) WAN (Wide Area Network) MAN ( Metropolitan-Area Network) LAN (Local Area Network) LAN is the most common type of network . LAN stands for Local area Network . It covers a small area. Most LANs are used to connect computers in a single building or group of buildings. Hundreds or thousands of computer maybe connected through LAN. Typical LANs can be found in industrial plants, office buildings, and college or university campuses. LANs are capable of transmitting data at very fast rate. Data transmission speeds of LAN are 1 to 100 megabits per second. It is much faster than data transmission over a telephone line. LAN can transmit data in a limited distance. There is also a limit on the number of...
9 comments
Read more

Ring topologies

Ring topologies are similar to bus topologies, except they transmit in one direction only from station to station. Typically, a ring architecture will use separate physical ports and wires for transmit and receive. Token Ring is one example of a network technology that uses a ring topology.
7 comments
Read more