A Shared Table System

A Shared Tables System
A shared table system is one where the data is stored in a central system (the server) and the program to manipulate the data is duplicated on multiple end-user computers. This is sometimes called a client-server system but is not as the file-server that holds the shared tables is doing nothing but pretending to be a disk drive.

Once again, Microsoft Access and all the other systems mentioned are an excellent choice of software for networked applications where the amount of data is small-to-medium or the number of simultaneous clients is small (less than 20). However Access tends to encounter difficulties in larger systems, due mainly to the way it locks records when two users wish to edit the same record. Along with Microsoft Access we must group C++, Visual Basic, Delphi and any other program which uses either Microsoft’s JET database engine, or Borland’s BDE engine as its core (and others).
 

Drawbacks of this type of system include:

• The network will encounter largish amounts of traffic as each client computer manipulates the data tables in turn. This is not a difficulty on a LAN but prohibits this architecture form being used on a WAN.
• If the database size is large, the amount of network traffic increases and the systems slows appreciably. Careful design needs to be undertaken to overcome this issue.
• Also, due to the nature of the data sharing, if any fault occurs, all users have to shut down and the system has to be restarted.
• These two issues are addressed in the true Client-Server system

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Advantages of a shared tables system include:

• Cheap, such a system uses the very same database items (MDB files in the case of MS Access) that a stand-alone system uses.  Usually very few alterations need to be made.
• Simple to scale-up from a single user system. The tables are separated into a new ‘database’ file and then they are just relocated to a separate location on a file server.
• This simplicity leads to very few costs being associated with this scale-up and generally very few defects are encountered due to the changes to the system.