CATASTROPHE-THEORY IMPLICATIONS FOR RIGHTSIZING WHEN PLANNING INTERIMSOLUTIONS FOR PROGRESSING FROM A PARTIAL MAINFRAME TO CLIENT-SERVER DISTRIBUTED DATABASES - 3D PREVIEWING OF POSSIBLE PROBLEMS

A planning method is presented, which we have used to analyse the impl ications of changes in key parameters for systems planning in consider ing the remote terminal access to a centralised system with a partial database as an interim path toward client-server systems. Calculations have provided a three-dimensional (3d) representation of the five par ameters of cost per transaction, distributed/centralised ratio and spe ed of server, cycles per transaction, and degree of multiprogramming. The 3d surface has a cusp properly which, if not appreciated visually, can lead to undesirable planning pathways of system sizing due to dis continuous effects in the catastrophe theory of such surfaces. A graph ic visual presentation, rather than text or tabular presentations, uti lises the great bandwidth that the visual system provides to the brain to assist in decision making and is used herein to increase awareness of planning features that are often not readily appreciated. The plan ning progression using a 3d visual application of the situation can al so logically lead to the stage for the decision between a distributed database system or a further extension of a centralised system, depend ing on transaction loads and the nature of database accesses required.