IT and Project Managment related Questions
Topic 1.4: The Historical Roots of Database: Files and File Systems Reasons for studying old file systems for data management • Although managing data through file systems is largely obsolete, understanding relatively simple charac teristics of file systems makes complexity of database design easier to understand.
• Awareness of problems that plagued f ile systems can help prevent similar problems when designing new databases, and • DBMS Knowledge of file systems is helpful if you plan to convert an obsolete file system to a DBMS Manual File Systems • Traditionally composed of collection of file folders kept in file cabinet • Organization within folders was bas ed on data’s expected use (ideally logically related) • System was adequate for small am ounts of data with few reporting requirements • Finding and using data in growing collect ions of file folders became time- consuming and cumbersome Conversion from Manual File System to Computer File System • Could be technically complex, requi ring hiring of data processing (DP) specialists • DP specialists created file struct ures, wrote software, and designed application programs • Resulted in numerous “home- grown” systems being created • Initially, computer file s were similar in design to manual files (see Figure 1.3) Basic File Terminology Note that the CUSTOMER file shown in Figure 1.3 contains 10 records. Each record is composed of nine fields:
C_NAME, C_PHONE, C_ADDRESS, C_ZIP, A_NAME, A_PHONE, TP, AMT, and REN.
Using the contents of the CUSTOMER file the DP specialist wrote programs for reports:
• Monthly summaries of types and amounts of insurance sold by agents • Monthly reports about which customers should be contacted for renewal • Reports that analyzed ratios of insurance types sold by agent • Customer contact letters summarizing coverage As time went on, additional reports we re written as required by the Sales Department. Another file called Sales was created to hold contents which helped track daily sales. Additional useful sales reports were generated\ for the Sales Department. Sales department st arted to feel the benefits and value of the generated useful reports for decision making.
Other departments such the Personal Department knew about the new automated Sales File System. So, they requested the DP Specialist to write or develop a new database to automate t he manual Payroll system for them. So, the DP Specialist has so far created:
• CUSTOMER database for the sales department • SALES database created for sales department • AGENT database created for personnel department As number of databases in creased, small file system evolved as shown in Figure 1.5 Each file used its own application programs Each file was owned by individual or department who commissioned its creation As system grew, demand for DP’s programming skills grew Additional programmers hired DP specialist evolved into DP manager, supervising a DP department The primary activity of department (and DP manager) remained programming The diagram shown in Figure 1.6 shows the more advanced database management system was evolved from the old file system.
Historical Background Computer Invention in the 1950s Data Processing Applications started in the 1950s Old File System software was used to implement and manage the data processing applications Old File System has problems Need for better Data processing and Managementsoftware Database Management System software Figure 1.6 Historical Background of the Old File System Concept Check What are the reasons for studying old file systems for data management?
