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Data Bases Development
Independent Databases
The Independent Databases can be related to the elementary DB,
cause it is possible simply to not consider many difficult questions.
Independent Database keeps data in the local file system, and database
machine which is carrying out access to them, located on the same computer.
Actually, Independent Databases are not used for the applications
requiring significant computing capacity, because the processor time
will be spent on performance of manipulations with data and in
whole will be lost for the applications.
The Independent Databases are useful to development of that application,
which are distributed among many users, and every user supports a separate database.
For example, application, which traces passed miles to define
indemnification for the spented fuel, could be created with use
of an Independent Database.
Each user of such an application could keep and manipulate the own data
about combustible on the own computer.
The user of this application does not have necessity to have a data access
of any other user, so the separate database here is quite acceptable.
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The Shared Databases do not differ from the Independent Databases,
except that they can be accessible to many clients through a network.
It makes them rather accessible, they can be manipulated from different
machines.
For example, let's take a database of the employee, mentioned in
the previous example.
If the manager change wage payment of the employee,
it will be marked by the application printing the receipts.
The computer that receives access to a database, starts the local
machine of such database.
Other advantage of Shared Databases is, that they don't make any
preliminary assumption of a network.
To the database machine is absolute indifferent, what type of network
is used - Novell, Banyan, Microsoft NT or anyone another,
because it examines a database simply as a file.
The Shared Database can appear improper only in a case, when it
is necessary execute a plenty of simultaneous admissions and
requiring calculations.
In this case decision is the Client/Server DB.
The exhausting decision of databases access problem is the Client/Server
model. In this case database access for the group of clients is carried
out by the special computer - server. Let's take, for example, a TAX
department database. The TD inspector can want to find out number of
the licenses of all persons earning more than $100.000 and paying less
than $2.000 of taxes. Actually, in the Shared Files system, it would
stops the requesting program, while viewing all extreme amount of the
data. In the Client/Server model the client asks the server to execute
the special task. It's the client business to decide whether to wait
for results, or to go to engage something more interesting. The server
is focused on operation with searches by the most optimum way. Though
the Client/Server architecture has the large advantage in productivity
and flexibility, it has also many lacks. The Client/Server decision
frequently appears more expensive, than decision with Shared Files.
Besides the Client/Server software requires the protocol, in which
there is a dialogue, such as TCP/IP. And though it frequently can
be made floppy enough, nevertheless, additional configuring and
administrative functions are necessary. Theoretically you can buy already available system, which has very floppy adjustment, but even it on occassion can't consult with your task. In this case we offer you to develop a Paradox, dBase or Access database under your concrete requirements, which is consult with any assigned task. |
