Objectives: Introduction Over View of System Analysis and Design
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- 10.2 Hardware Selection
- 10.3 Determining size and capacity requirements
| 10.1 Introduction A major element in building systems is selecting compatible Hardware & software. The kind of hardware & peripherals required is to be determined. The suitable software has to be selected. The experienced analysts will explore various options regarding it. Hardware/software selection begins with requirements analysis, followed by a request for proposal and vendor evaluation. The final system selection initiates contract negotiations, price, maintenance agreements, vendor selection, acceptance criteria and similar issues. 10.2 Hardware Selection Gone are the days when a user calls IBM to order a 360 system, which in itself included hardware, software & support. Today, selecting a system is a serious and time concurring activity. Unfortunately, many systems are still selected based on vendor reputation only or other subjective factors. Instead the factors, which are to be considered, should be determining equipment size, capacity needs, financial considerations and acquisition method. 10.3 Determining size and capacity requirements With computers ranging in size from small microcomputers to large mainframe systems, the number of options to choose from when selecting a system is obviously very large. Even within the lines of a single manufacturer, there are many different models and configurations from which to select. How then does the analyst determine which system to use when anew computer is to be acquired The starting point in an equipment decision process is the size and capacity requirements. One particular computer system maybe appropriate for one workload and inappropriate for another. Systems capacity is frequently the determining factor. Relevant features to consider include the following 1. Internal memory size 2. Cycle speed of system for processing 3. Characteristics of display and communication components 4. Types and numbers of auxiliary storage units that can be attached 5. Systems support and utility software provided or available Frequently, software needs dictate the minimum configuration required. For instance, if a particular program to be run on a microcomputer requires, say, 4 megabytes of storage, the list of feasible candidates will exclude all systems, regardless of their attractiveness, that do not have or that cannot be easily configured to have a memory of at least 4 megabytes. All systems have limits, depending on what they are designed for. The limits mayor may not be a factor in a particular selection decision. For example, some systems communicate data only in asynchronous fashion. If the system has other attractive features and will not be used for data communications or teleprocessing, the synchronous feature maybe of little concern. However, if the primary application for the computer requires synchronous transmission of ASCII data, the bisynchronous limitation is important. Likewise, the fact that a particular minicomputer is limited to five ports for connecting terminals and printers maybe too restrictive in a teleprocessing system designed to link 23 sites together through terminals and communications lines. Software needs often dictate hardware requirements such as internal memory sizes, communication ports, disk capacity, and the ability to use magnetic tape. Vendors are reliable sources of configuration requirements. They can provide information on the minimum configuration requirements needed to use their software properly. Trade newspapers and magazines provide regular distribution of information about hardware and software requirements. In addition, subscription services offer information on operating specifications. These services, which cost several hundred dollars yearly, provide monthly updates (generally using a loose-leaf binder format) and telephone assistance for computer operation, as well as user comments. Auxiliary storage capacity is generally determined by file storage and processing needs. To estimate the disk storage needed fora system, the analyst must consider the space needed for each master file, the space for programs and software, including systems software, and the method by which backup copies will be made. When using flexible diskettes on a small business system, the analyst must determine whether master and transaction files will be maintained on the same diskette and on which diskette, programs will be stored. Backup considerations, as well as file size, guide the decision about how many disk drives are needed. The configuration should keep scope for backup copies of all disks. Download 0.94 Mb. Share with your friends:
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