The starting point of every purchase of a client/server DBMS is to define the objective and design of the whole system as these dictate the considerations required to ensure information system success. This, of course, is always subject to budgetary constraint and acceptable specification and performance compromises often result from the ideal solution.
In my experience, we specify the client/server DBMS based on the maximum we can achieve (performance, features) and then scale this based on budgetary constraints versus user acceptability. This is no mean task as results are often difficult to gauge until decisions have been made and purchase contracts committed to, hence the solution should always be flexible enough to allow for changes (often done by flexible arrangements with 3rd party providers, something that is not always easy to achieve).
With this in mind the chosen client/server DBMS needs to strive for:
• Suitability: must be able to provide the features that the overall design requires and the skills available in the market must not be a critical issue.
• Robustness: must be reliable under ordinary operating circumstances and able to operate under a Service Level Agreement (SLA) for support.
• Independence: must by compatible and must not be reliant on any component of any system that would render the information system any less usable or useful should that component or system change technically or have a budgetary impact or cease to be supported.
• Flexibility: the system must be able to be extended and adapted if required by changing objectives (within reason).
• Experience: we must use the skills and experience of our people and take advantage of any positives from existing systems.
• Efficiency: the system must place a minimum overhead on hardware resources (including communication lines).
• Performance: the system must operate well within expected response times under worst case scenarios.
• Usability: the system must be easy to use for all levels of users regardless of system permissions and requirements.
• Business Continuity: the system must be able to be re-established without the loss of data in an acceptable time (again covered by agreed SLA). This includes data replication and backup/restore procedures.
Without the consideration of all of these factors and an acceptable compromise being made, it is likely that the chosen client/server DBMS will fail its objectives.
Coronel, Morris & Rob (2009) Database Systems: Design, Implementation, and Management (9th Edition). Cengage Learning.
Bakar, J (2009) Purchasing Software and DBMS [Online]. Available at http://www.scribd.com/doc/26840751/Purchasing-Software-and-DBMS (Accessed 16 May 2010).