Reduces the amount of duplicated data in different files.
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What is Data Inconsistency?
When data is stored in many files and each file has to be updated individually every time the data is changed.
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What is a Database?
a collection og non-redundant data shareable between different applications.
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What were problems before Databases were created?
Data Redundancy, Data Inconsitency, Program-data dependant, lack of flexibility, un-sharable data, unproductive maintenance and also Lack of security.
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What is a DBMS?
Database Management systems are used to improve security and eliminate unproductive maintenance.
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What is a DBMS?
It is software that is used to control access to the data.
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What are two essential features of a DBMS?
1. Program-data independance; the storage structure is hidden from each user. 2.Restricted User Access; each user is given a limited view of the data, according to the need.
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What is the Three Level architecture of a DBMS?
1. External/User Scheme 2. Conceptual or Logical Schema 3. Internal or Storage Schema
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What is the External or User Schema?
Individuals view of the database
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What is the Conceptual or Logical Schema?
Overall view wof the database, including entities, attributes and relationships.
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What is Internal or Storage Schema?
Describes how the data will be stored.
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What is Data storage, retrieval and update?
The DMBS must allow users to store, retrieve and update information as easily as possible. There is also Creation and Maintenance of the data dictionary
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What is 'Managing the facilities for sharing the database'
Has to ensure that problems do not arise when two people access a record.
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What is 'Back Up and Recovery'
Must provide ability to recover the database in event of system failures.
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Security
Must handle password allocation and checking.
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What is a Multi Access Database?
1. More than 1 person can use the program at the same time. 2. Users can work with databases which are stored on shared drives
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What does 'Ensuring the integrity' mean?
Making sure that no data is accidentally lost or corrupted.
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How does 'opening the entire database in exclusive mode' help?
It prohibits all simultaneous access. It is impractical when several users need to acess it, but will give the fastest performance because it doesnt have to search for potential confilcts.
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How does 'Locking all the Records being modified' help?
the moment that a user opens, the software will prevent any other user opening the same table in any view that would allow updating.
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How does 'Locking the record from being Edited' help?
The moment the user first starts typing, the record will automatically be locked so that noone else can update it
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How does 'The user specifies no locks' help?
It is up to the software to ensure that the users are aware of the situatio, when it is being simultaneously updated by two computers.
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How does 'Open a table in Read Only mode' help?
If you dont need to update a table, but look at a record, you can avoid conflict by opening it in Read Only mode.
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What is Deadlock?
When two users attempt to update two related records in the same table. The DBMS must recognise this and abort one of the users tasks, to allow the other to proceed.
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What are software protection techniques?
1. Name Identify 2. Each will have a password 3. Encryption
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What are Open Systems?
Open systems provide a standard to which applications are written to allow portability to multiple systems. The portability is Key.
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What is an ODBC (Open Database Community)
ODBC is a standard for accessing different database systems. It provides a means of accessing data help in one type of database. The ODBC translates requests into the correct format for aparticular source. It is extremely useful.
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What is a Client Server Database?
DMBS client software runs on individual workstations. The advatanges of these are an expernsive resource can be available to large number of users , client stations can also update thedatabase, communication between client and server is minimised.
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What are Object Orientated Databases?
They offer DBMS facilities with object-orientated programming. Data stored as objects can only be interpreted using the methods specified by its class.
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Other cards in this set
Card 2
Front
What is Data Inconsistency?
Back
When data is stored in many files and each file has to be updated individually every time the data is changed.
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