[Year 12 IPM] Redundancy

[Robert Hind]

Data redundancy is the repetition of the same data more than once within a 
system. I don't agree with the suggestion that dob and age fields in the 
same table constitute data redundancy (or the inclusion of hours worked, pay 
rate and total earned). Both fields may not be needed and in fact the age 
field would need to be updated each year so a more effective and efficient 
method would be to store dob only and calculate the age each time you access 
the data, eg using a calculated field in a query in Microsoft Access. But 
not really DR to my mind.

I also suggest that backup is a separate function and should not be confused 
with DR within a data system.  RAID? Ok, planned, on-the-fly, DR for data 
security in case of system failure.

Robert Hind
IT/Physics/Maths teacher
Ashwood College
hind.robert.m at edumail.vic.gov.au





----- Original Message ----- 
From: "Mark Kelly" <kel at mckinnonsc.vic.edu.au>
To: "Year 12 Information Technology Processing and Management 
Teachers'Mailing List" <ipm at edulists.com.au>
Sent: Wednesday, October 12, 2005 1:29 PM
Subject: Re: [Year 12 IPM] Redundancy


Data redundancy (DR) can be good and bad.

When bad, it wastes storage space or blows out the size of a data
structure with no benefit (e.g. as previously mentioned, the same data
stored in 2 tables in a database).  I suppose DR can even mean the same
data stored in multiple copies of the same file.  Database normalization
can help fix DR.

On the positive side, DR can be good.  Backups are classic examples of
DR.  Backup servers or backup data hosts which take over in case the
primary host fails) are DR.  RAID's mirroring is DR.

Dunno if that helps anyone  :-o

Andrew Sutton wrote:
> Doesn't it also have to do with two fields in the one table that are
> essentially giving you the same information? For example, In a table, You
> shouldn't need the Age field if you have an accurate D.O.B. field.
> -----Original Message-----
> From: ipm-bounces at edulists.com.au [mailto:ipm-bounces at edulists.com.au] On
> Behalf Of Geraldine McKenna
> Sent: Tuesday, 11 October 2005 11:41 PM
> To: Year 12 Information Technology Processing and Management
> Teachers'MailingList
> Subject: [Year 12 IPM] Redundancy
>
> Hi everyone,
> Thanks for the help this list has provided throughout the year again!! 
> Could
> someone plese explain to me the meaning of 'data redundancy'? My
> understanding is that it relates to loss of data and I also think it is
> different to 'data integrity' but am not clear about these. It has come up
> as a result of students having just completed the Insight Trial Exam 
> paper.
> Thanks in advance.
> Geraldine McKenna
> IT Coordinator
> Avila College
> Mt Waverley
>
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-- 
Mark Kelly
Manager - Information Systems
McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria Australia
Phone +613 95780844  Fax +613 95789253
http://www.mckinnonsc.vic.edu.au
IPM Lecture notes: http://vceit.com
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Important - 
This email and any attachments may be confidential. If received in error, please contact us and delete all copies. Before opening or using attachments check them for viruses and defects. Regardless of any loss, damage or consequence, whether caused by the negligence of the sender or not, resulting directly or indirectly from the use of any attached files our liability is limited to resupplying any affected attachments. Any representations or opinions expressed are those of the individual sender, and not necessarily those of the Department of Education & Training.