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| Migration: |
In a nutshell...
Migration is the term that is used for moving data
from one system to another.
For example: Your data may reside
in an old legacy database and you want to upgrade
to a new system or, you may have data stored in
Microsoft Excel Workbooks and want to have the extra
integrity and functionality that a database can
give you.
Tell me more...
People usually migrate data from one system to another
when they realise their existing system is not up
to the task in hand and by moving to a better system
they will increase their businesses efficiency.
The difficulty of the migration will depending on
the source of the data. In general, there are only
two sources of data that need to be considered.
The first is data that comes from an existing database
and the second source is from anywhere but a database.
Source of data - Database:
If the source of your data is from an existing database,
the process is going to be far easier than from
any other source. This is because databases follow
a set of rules for storing data and these rules
are consistent between databases. (Note: This is
only true if the rules in the source database were
correctly applied).
If the rules were adhered too, then the migration
should be relatively painless. The person migrating
the data will most likely have to to make changes
to the existing data or even add more data before
it can be exported so that it conforms to the structure
and validation rules of the new system.
During the migration, it's often a good idea to
clean up the data before it's allowed into the new
system. For example, maybe the old system didn't
enforce the adding of a postcode when an address
was added. You may want to hold back from inserting
these records until you have run them though a postcode
validating process such as the PAF system used by
the Royal Mail postal company.
Source of data - Other:
This is where the real fun begins. Any data you
have that's not part of a database is going to mean
more work.
A common migration I perform is from Microsoft Excel.
Excel is a very useful tool that allows users to
enter data into something very quickly. The problem
is, Excel allows you to break every rule in the
book when it comes to storing data properly.
The migration of data from non database systems
is painful and expensive but ultimately it will
be worth it.
Anything else?
Do you have to migrate the data? Is it possible
to run a new system and keeping the old system for
reference? Depending on the situation, sometimes
it's just not worth trying to migrate data.
For example, lets say I started a fruit and vegetable
shop and I kept all my records in a spreadsheet.
Six months later I realise the limitations of the
spreadsheet and decide to use a database instead.
What difference does it make to include the data
from the last six months? Sure it would be nice
to have it, but does the cost outweigh the benefit?
If ever I need that information, couldn't I just
interrogate my old spreadsheet?
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