Logical and Physical Design

LOGICAL AND PHYSICAL DESIGN

System design goes through two phases of development: Logical and Physical Design. When analyst prepare the logical system design, they specify the user’s needs at the level of detail that virtually determine the information flow into and out of the system.

The design covers the following :

  • Reviews the current physical design: its data flow, file contents etc.
  • Prepare Output Specification: determine the format, content and frequency of reports including terminal specifications and locations.
  • Prepare Input Specification: format, content and most of the input functions. This includes determining the flow of the document from the input data source to the actual input location.
  • Specifies the implementation plan.
  • Prepare edit, security and control specification: this include specifying the rules of edit correction, backup procedures and file integrity.
  • Prepare a logical design walkthrough of information flow, output, input controls and implementation plan.
  • Reviews benefits, costs, target dates and system constraints.

Following logical design is physical design. This produces the working system by defining the design specification that tells the programmers exactly what the candidate system must do. The programmer writes the necessary programs or modifies the software package that accepts input from the users, performs the necessary calculations through the existing files or databases, produces the report on a hard copy or displays it on screen.

Physical system design consists of following steps :

  1. Design the physical system-
  • Specify input/output media.
  • Design the database and specify backup procedures.
  • Design physical information flow through the system and physical design
  1. Plan System implementation-
  • Prepare a target date and a conversion schedule.
  • Determine training procedure, courses and time tables.
  1. Specify any new hardware/software.
  2. Update benefits, costs, conversion date and system constraints (legal, financial, hardware etc.)

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