ICT in Data Management

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ICT in Data Management
 Database = collection of fields and records
 A DBMS (Database Management Software)
manages the database by ;

 Setting
the
Relating
Querying
the
/ Structure
Interrogating
files
the records

Year 12 Applied ICT –Premier Academy © February2011

1

ICT in Data Management
Sequential Files


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
2. Update is only possible if new record is the same
length
3. Processing records is slow as one has to go through
all records that are before the one required
Year 12 Applied ICT –Premier Academy © February2011

2

ICT in Data Management
Processing of Sequential
1.3.
Changing
a New
Modifying
Record a Record
2.Addind
Deleting
a /Record
Files
- Master and Transaction files are run together

- - Keyfields
of both
are compared
Masterand
and
Transaction
filesare
arerun
runtogether
together
- Master
Transaction
files
- - The
lower keyfied
is written on new master file
Keyfields
are compared
- Match
is found
-- Process
continues
till is
theignored
end is reached
The onewith
to
be
deleted
- Record
new
details
in transaction file is written instead
- Next field is written on new master file

Year 12 Applied ICT –Premier Academy © February2011

3

ICT in Data Management
LESSON 2

Indexed Sequential Files
Random Access/Direct
Files

Hierarchical Database Management
Systems
Network Database Management
Systems
Relational Database Management
Systems
Year 12 Applied ICT –Premier Academy © February2011

4

ICT in Data Management
Indexed Sequential Files


Records are stored in order eg. by surname on disk for
direct access.



Each record has a fixed size.



Index table shows where on disk record is stored eg. 1 to 26
(A to Z) ;1=A records, 2=B records………



Example: To read a record starting with “S”, all records from
“A” to “R” are ignored. All from “S” have then to be gone
through . This allows faster access eg. batch processing of
employee records.




Random Access/Direct
Is the fastest access method
Files
Uses magnetic disks and keyfields
Year 12 Applied ICT –Premier Academy © February2011

5

ICT in Data Management
Hierarchical Database
Management Systems


Are no longer used as they cannot relate many files



Uses tree structure with few files at top and more below



Used in file organisation of computer folders/files
Advantage



Fast file access
Disadvantage



One bypasses a lot of data while going down the directory

Year 12 Applied ICT –Premier Academy © February2011

6

ICT in Data Management
Network Database
Management Systems



Are no longer used



Uses two methods;
Method 1



Different parts of the database are stored in separate linked
computers 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.
Method 2



Whole database is stored on one computer but accessed by
many users of the network eg. Police computer database

Year 12 Applied ICT –Premier Academy © February2011

7

ICT in Data Management
Relational Database
Management Systems


Separate files are related together



Fields can be picked from different tables to make reports
Advantage



No repetion thus less storage space



Faster data retrieval as the files are linked



More secure- the data is not duplicated thus less chance of
hacking



Easy to expand / add more tables
Disadvantage



Becomes complex as it is expanded

Year 12 Applied ICT –Premier Academy © February2011

8

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