ICT in Data Management

8/18/2019 ICT in Data Management

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ICT in Data Management

Year 12 Applied ICT –Premier Academy © February2011 1

Database = collection of fields and records

A DBMS (Database Management Software)

manages the database by ;

Setting the Structure Relating the files uerying ! "nterrogating the records


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Year 12 Applied ICT –Premier Academy © February2011 #

$ Records are stored one after another as they are added

$ They are sorted by keyfield (sequential) on magnetic tape

$ Unsorted files are called serial files

Disadvantages of Sequential files

1 Records can only be added at the end

! Update is only possible if ne" record is the same

length

# $rocessing records is slo" as one has to go through

all records that are before the one required

Sequential Files


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Year 12 Applied ICT –Premier Academy © February2011 %

% &aster and Transaction files are run together

% 'eyfields of both are compared

% The lo"er keyfied is "ritten on ne" master file

% $rocess continues till the end is reached


% 'eyfields are compared

% The one to be deleted is ignored

% et field is "ritten on ne" master file


% &atch is found

% Record "ith ne" details in transaction file is "ritten instead

1 *ddind a e" Record! Deleting a Record# +hanging , &odifying a Record

Processing of Sequential

Files


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Year 12 Applied ICT –Premier Academy © February2011 &

Relational Database ManagementSystems

Indexed Sequential Files

Random Access/Direct

Files

Hierarchical Database ManagementSystems

et!or" Database ManagementSystems

LESSON 2


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Year 12 Applied ICT –Premier Academy © February2011 '

$Records are stored in order eg by surname on disk fordirect access

$ -ach record has a fied si.e

$ /nde table sho"s "here on disk record is stored eg 1 to !0

(* to ) 213* records4 !35 records666$ -ample7 To read a record starting "ith 8S94 all records from

8*9 to 8R9 are ignored *ll from 8S9 have then to be gone

through This allo"s faster access eg batch processing of

employee records

$ /s the fastest access method

$ Uses magnetic disks and keyfields

Indexed Sequential Files

Random Access/DirectFiles


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Year 12 Applied ICT –Premier Academy © February2011

$ *re no longer used as they cannot relate many files

$ Uses tree structure "ith fe" files at top and more belo"

$ Used in file organisation of computer folders,files

*dvantage

$ :ast file access

Disadvantage

$ ;ne bypasses a lot of data "hile going do"n the directory

Hierarchical Database

Management Systems


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Year 12 Applied ICT –Premier Academy © February2011

$ *re no longer used

$ Uses t"o methods2

&ethod 1

$ Different parts of the database are stored in separate linkedcomputers but the database appears as a single unit

$ Since some parts are duplicated it is a form of backup and

also offers fast access to data

&ethod !

$


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Year 12 Applied ICT –Premier Academy © February2011 *

$ Separate files are related together

$ :ields can be picked from different tables to make reports

*dvantage

$ o repetion thus less storage space

$ :aster data retrieval as the files are linked

$ &ore secure% the data is not duplicated thus less chance of

hacking

$ -asy to epand , add more tables

Disadvantage

$ 5ecomes comple as it is epanded

Relational Database

Management Systems

Documents

ICT in Data Management