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IT 450 MIDTERM
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Exam of 5 pages for the course CHEM 162 Final at CHEM 162 Final (IT 450 MIDTERM)
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IT 450 MIDTERMWhat are the main characteristics of database technology? - correct answer-. The database
system contains not only the database itself but also a complete definition of the database.
The definition is stored in the system catalog. In traditional file processing, data definition is
part of the application
programs.
. Self-contained nature of a database system: A DBMS catalog stores the description of the
database including structure, types and format. The description is called meta-data. This
allows the DBMS software to work with different databases.
. In traditional file processing, the structure of files is embedded in the access program,
changes to the structure of files require changing the program that accesses the file. In
DBMS, just change the description in the catalog, no access programs are changed.
Program-Data Independence - correct answer-Insulation between programs. Allows
changing data storage structures
without having to change the DBMS access programs
Data Abstraction - correct answer-A data model (a type of abstraction) is
used to hide storage details and present the users with a conceptual view of the database.
AKA:
Program-data independence/
program-operation
Data vs. Information - correct answer--DATA is raw, unorganized facts that need to be
processed. Data can be something simple and seemingly random and useless until it is
organized.
ex: Each student's test score is one piece of data
-INFORMATION is when data is processed, organized, structured or presented in a given
context so as to make it useful, it is called Information.
ex: The class' average score or the school's average score is the information that can be
concluded from the given data.
What are the short comings of file processing systems? - correct answer-. Duplication of
data and data inconsistency
. Difficulty in accessing data
. Limited data sharing
. Integrity problem
. Atomicity problem
, . Concurrent-access anomalies
. Lengthy development times
. Security problem
. Excessive system maintenance
Database Management System (DBMS) - correct answer-A software package to facilitate
the creation and maintenance of a computerized database.
Its function includes:
. Defining a database--specifying the data types, structures,constraints for the data to be
stored in the database.
. Constructing a database--a process of storing the data on medium.
. Manipulating a database--querying to retrieve data, updating database, generating reports.
Data dictionary system - correct answer-Used to store catalog information about schemas
and constraints, as well as design decisions, application program descriptions, user
information, usage standards, etc.
Active data dictionary - correct answer--a combined catalog/data dictionary
-is automatically updated by the DBMS with every database access to keep its access
information up to date
-is accessed by DBMS software and users/DBA
Passive data dictionary - correct answer--is not updated automatically and usually requires
running a batch process.
-is accessed by users/DBA only
system catalog - correct answer-a detailed system data dictionary that describes all objects
within the database
*What are the 3 types of data model categories?* - correct answer-1)Conceptual (high-level,
semantic)
2)Physical (low-level, internal)
3)Internal (representational, record-oriented)
Conceptual data models (designers view) - correct answer--high-level, semantic
-Provide concepts that are close to the way many users perceive data.
-includes entity-based or object-oriented data models.
Physical data models - correct answer--low-level, internal
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