Chapter 10 Presentation

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MODEL OF THE FIRM
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DATABASE
APPLICATION PROGRAMS
DBMS
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Database Data

• The data contained in a database includes an
  accumulation of most of the facts about data
  types that depict conditions facing the firm
  required to understand the many different areas
  in the firm.
• Individual data items for data types typically
  reside in a single storage location within disk
  storage provided for the database.

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Database Creation Using Logical Objects
The DBA uses the logical objects of the business,
as defined in entity type descriptions while
creating E/RDs, to create a database in correct
format and relatively free from errors.
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Data Integration

• Refers to the ability to consolidate data items
  from different database files to reconstruct
  logical objects from database objects as either
  input or output to the IS or an online user
  inquiry.
• The DBMS establishes data integration by how it
  "defines" the database in relation to the
  database's logical database structure, as
  perceived by users, and the physical database
  structure that defines how data is physically
  stored in the database.

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Finding Logically Related Data by Using Database
Names

• By using schema section and data item naming
  conventions, logically related data can be
  physically found by referring to its section name
  (file name) and specific data item names (field
  name).

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Schema Used to Locate Data Items in the Database

• The DBMS uses the schema to integrate the logical
  view and physical view of data in the database to
  permit access of data items stored in completely
  different physical locations in such a way that
  the data appears to be physically stored
  together.
• Programs in systems and online user access
  commands can retrieve logically related data
  items without considering that the data comes
  from completely different physical locations.

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Database Administrators (DBA)

• DBAs Direct the DBMS to create and maintain
  databases.
• DBA Functions
• Direct the DBMS to create or modify the schema.
• Define user views.
• Manage all activities affecting the database.
• Manage the DBMS Perform economic analysis
  concerning the database environment.

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DBA Creation ofthe Database Schema

• The DBA directs the DBMS to define the database
  schema by assigning names to database files and
  data items in relation to the database design
  that best complies with the user requirements
  derived by the analyst.
• The DBA directs the DBMS to create the schema by
  issuing commands in a command language used to
  communicate with the DBMS.

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Data Definition Commands (DDC)

• DBAs use certain commands within the command
  language, called data definition commands (DDCs),
  to direct the DBMS to create or modify the
  schema.
• EXAMPLE The CREATE or MODIFY commands in dBASE,
  a desktop computer DBMS, are DDCs that create or
  modify a database schema.

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User views

• Specifications that identify the portions of the
  database a user can access and whether that user
  can perform modifications on the data items
  included within that user view.
• The DBA defines user views for each class of
  qualified users that specify what they can access
  and if they can update the portion of the
  database they can access.
• DBAs identify user views by determining the
  logical objects that satisfy the users
  information needs and determining in which
  database objects the properties of these logical
  objects reside.

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Economic Analysis

• The DBA performs economic analysis on the
  functioning of the DBMS, performance of network
  hardware and software, operations of the control
  software systems, access to data in the database,
  density of data in specific storage areas, and
  the functioning of utility and application
  software systems that use the database.

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Management of Database Activities

• The DBA is responsible for managing all
  activities affecting the database by establishing
  an environment conducive for successful and
  authorized completion of these activities.

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System Tuning

• The DBA uses statistical information related to
  DBMS actions to sample the execution of DBMS
  directing functions and investigate user
  complaints about response time and validity of
  accessed information to determine where changes
  should occur to alleviate problems.
• The statistical analysis often causes them to
  disperse data among different storage devices for
  increased efficiency (tuning the system).

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Possible DBA Directed Changes to the Database
Technology and Environment

• How the data is dispersed (system tuning).
• An update of the DBMS itself.
• Changing application programs.
• Modifying or replacing the current communication
  software.
• Training users in proper accessing methods.
• Changes to the specific configuration of
  hardware and software.

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DBA AID with Regard to Hardware/Software
Configuration

• Reconfiguring hardware system for better
  efficiency and effectiveness.
• Reconfiguring the communication control system
  for better data access and data distribution.
• Better DBMS application program interaction.
• Better use of operating system as a fundamental
  control system.
• Better use of storage devices on which the
  database is used.

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Client-Server Computer Architecture

• Encompasses using host computers (Minicomputers
  and mainframes) to access centrally stored
  databases to pass the database request to client
  computers (typically desktop computers), and
  using client computers to perform the actions on
  the retrieved data.

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Data Structure Relationships for Data Objects

• Tree (or hierarchical) relationship.
• Simple network relationship.
• Complex network relationship.

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Tree Relationship (Hierarchical Relationship)

• A relationship that specifies a one-to-many (1M)
  relationship between data objects in a data type
  on the ONE side (Parent) related to many data
  objects of the data type on the MANY (Child) side
  of the relationship, and the data objects on the
  many side are only related to one data object on
  the one side of the relationship.
• A one-to-one (11) relationship between data
  objects is considered a special purpose 1M
  relationship wherein both sides of the
  relationship are single data objects linked to
  single data objects.

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Simple Network Relationship

• A data relationship wherein the parent data types
  have one-to-many relationships with corresponding
  child data types, but child data types may have a
  relationship with multiple parents as long as the
  parents are from different data types.

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Complex Network Relationship

• A data relationship wherein parent data objects
  may have a relationship with many child data
  objects, and a child data object may have a
  relationship with many parent data objects (even
  parents of the same data types), eg. a many-to-
  many (MN) relationship.

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Database Data Structuring Relationships

• Tree
• Vendorlt------------------gtgtInvoices
• Simple Network
• Vendorlt----gtgtInvoicesltlt----gtCustomers
• Complex Network
• Vendorltlt-----------------gtgtInventory items

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Database Data Structures and E/RD Specifications

• DBAs identify the type of relationship between
  different data types by reviewing the cardinality
  relationship (11 - 1M -MN) between the
  entities that represent the data types on an E/RD.

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Models for Commercially Available DBMSs

• Hierarchical (Tree) model.
• Network (Simple Network) model.
• Relational (Complex Network) model.
• Hierarchical Database Models are those DBMSs that
  define data relationships using trees.
• Network Database Models are those DBMSs that
  define data relationships using simple networks.
• Relational Database Models are those DBMSs that
  can more easily define data relationships using
  complex networks.

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Hierarchical and Simple Network-based DBMSs

• DBMSs based on the hierarchical or network
  database model can model higher level
  relationships by decomposing the higher level
  relationships into multiple trees or simple
  network relationships, respectively.

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The Relational Model

• The Relational Model conceptually portrays the
  data contained in the database as a large table.
• The Relational Model refers to the subsections
  (files) of the database (table) by the name
  relation to individual data items (fields) in
  these subsections by the name attribute and to a
  collection of individual data items that depict a
  real-world object by the name occurrence (record).

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Database ManagementSystem Functions

• Create the database, including its schema.
• Store, retrieve, and update data contained in the
  database.
• Provide for the integrity of the data contained
  in the database.
• Secure the database from unauthorized entry
  and/or invalid modification.
• Synchronize of user accesses.
• Crash protection and recovery from failure.

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Access Synchronization

• The DBMS typically ensures that the concurrent
  access of the same data item by different users
  is synchronized by reserving (locking) portions
  of the database from access by other users while
  updating actions are performed.

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Database Crash Protectionand Recovery

• The DBMS provides for crash protection and
  recovery from failure by creating a periodic
  backup of the database and reapplying updating
  accesses to the database.

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Journal Files

• Files used to store all updating accesses that
  occur during the period between database backup
  executions.
• After a database is destroyed or rendered invalid
  through some event, journal file update entries
  are reapplied to the previous backup copy of the
  database during database reconstruction.

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Data Manipulation Commands (DMCs) and Command
Languages

• The DBMS's communication language (described
  earlier) also has commands called data
  manipulation commands (DMCs) used to cause the
  DBMS to access appropriate data values within the
  database.
• Database inquiries require a syntactically
  (grammatically) correct DMC to retrieve the data
  values referenced by designated names within the
  DMC.

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Online Database Access

• Users use on-line database access (queries) to
  gain access to information in lieu of what is
  normally supplied to them by the firm's IS, gain
  quicker access to information the IS does supply,
  directly receive reports on data values within
  the database, or perform direct updates when
  unusual sets of events occur within the firm's
  operations.

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Preprogrammed Database Accesses and Screen Masks

• IS personnel often create preprogrammed commands
  and/or screen masks to access the database in a
  user friendly method for user issued queries.
• These preprogrammed accesses are typically
  constructed by creating a program of DMCs.

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Client Computer Database Access Commands

• Users can issue DMCs from client computers to a
  DBMS residing on a server computer to direct the
  server DBMS to retrieve the data from the
  database and return these data values to users on
  their desktop, client computers.

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Interfacing Computer Systems to the Database

• Most data used by computer systems is retrieved
  from the database by issuing I/O DMCs.
• The client computer application program is called
  a host program because it contains (hosts) DMCs
  to be sent to the DBMS.

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Logical Data Structures from Physical Data
Structures

• Logical data types illustrated in the
  Enterprise/Methodology Model typically consist of
  data items from a number of physical data types
  in the database.

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Reconstructing Logical Data Objects from Database
Objects

• DMCs often cause the DBMS to reconstruct the
  logical data type (Entity Type Description) from
  the DATABASE OBJECTS to create the PROGRAM VIEW
  OF LOGICAL OBJECTS as illustrated on the
  enterprise/Methodology Model.

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