1. 1 Systems Support Introduction  The chapter will address the following questions:  What is systems support?  What is the role of a repository in systems support?  What is the difference between maintenance, enhancement, reengineering, and design recovery?  What is the maintenance challenge presented by the year 2000?

2. 2 Systems Support What is Systems Support?  Introduction  Systems support is the on-going maintenance of a system(s) after it has been placed into operation. This includes program maintenance and system improvements.  Systems support often requires developers to revisit activities typically performed in systems analysis, design, and implementation.

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4. 4 What is Systems Support?  Introduction  There are three distinct types of system-level data storage.  Central repository. This repository stores all system models and detailed specifications. Subsets of the central repository are checked out to support various planning and development projects. These subsets are stored as project repositories, usually implemented through various CASE tools.  Program libraries. Store the actual application programs that have been placed into production. In most shops, a software-based librarian will track changes and maintain a few previous versions of the software in case a problem arises with a new version.

5. 5 Systems Support What is Systems Support?  Introduction  There are three distinct types of system-level data storage. (continued)  Business databases. Store the operational data created and maintained by the production application programs.  Systems support is primarily driven by systems designers and system builders in support of system users.

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7. 7 Systems Maintenance - Correcting Errors  Introduction  Regardless of how well designed, constructed, and tested a system or application may be, errors or bugs will inevitably occur.  The correcting of bugs is called system maintenance, or program maintenance.  The fundamental objectives of system maintenance are:  To make predictable changes to existing programs to correct errors that were made during systems design and implementation. Consequently, we exclude enhancements and new requirements from this activity.  To preserve those aspects of the programs that were already correct. Inversely, we try to avoid the possibility that ``fixes'' to programs cause other aspects of those programs to behave differently.

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9. 9 Systems Maintenance - Correcting Errors  Define and Validate the Problems  The first task of the assigned team is to define and validate problems.  This activity will be facilitated by the analyst and/or programmer, but it should clearly involve the user(s).  The problem programs are retrieved from the program library.  Working with the user(s), the team should attempt to validate the problem(s) by reproducing it.  If the problem cannot be reproduced, the project should be suspended until the problem reoccurs and the user can explain the circumstances under which it occurred.  In some cases the bug arises from simple misunderstandings or misuse, and corrective instructions can bring the entire project to closure.

10. 10 Systems Support Systems Maintenance - Correcting Errors  Benchmark the Programs and Application  The program(s) isn't all bad, or it would have never been placed into production in the first place.  System maintenance can result in unpredictable and undesirable side effects that impact the programs or application's overall functionality and performance.  Before making any changes to programs, the programs should be executed and tested to establish a baseline against which the modified programs and applications can be measured.  This step is performed by the systems analyst and/or programmer.  The users may also participate.

11. 11 Systems Support Systems Maintenance - Correcting Errors  Understand the Application and its Programs  Frequently, system maintenance is not performed by the same persons who wrote the program.  For this reason, we need to gain an understanding of the application and the problematic programs.  Application and program knowledge usually comes from studying the source code from the benchmarked programs.  Program understanding can take considerable time.  This activity is slowed by some combination of the following limitations: Poor modular structure. Unstructured logic (from prestructured era code). Prior maintenance (quick fixes and poorly designed extensions).

12. 12 Systems Support Systems Maintenance - Correcting Errors  Understand the Application and its Programs  This activity is slowed by some combination of the following limitations: (continued) Dead code (instructions that cannot be reached or executed -- often leftovers from prior testing and debugging). Poor or inadequate documentation.  The purpose of application understanding is to see the big picture - - that is, how the programs fit into the total application and how they interact with other programs.

13. 13 Systems Support Systems Maintenance - Correcting Errors  Understand the Application and its Programs  The purpose of program understanding is to gain insight into how the program works and doesn't work.  You need to understand the fields (variables) and where and how they are used, and you need to determine the potential impact of changes throughout the program(s).  Program understanding can also lead to better estimates of the time and resources that will be required to fix the errors.

14. 14 Systems Support Systems Maintenance - Correcting Errors  Edit and Test the Programs  Given application and program knowledge and validated changes, the programmer can now make changes to the programs to be modified.  There is a big difference between editing a new program and editing an existing program.  Changes that you make may have an undesirable ripple effect through other parts of the program or, worse still, other programs in the application.  The following tests are essential and recommended:  Unit testing (essential) ensures that the stand-alone program fixes the bug without side effects.

15. 15 Systems Support Systems Maintenance - Correcting Errors  Edit and Test the Programs  The following tests are essential and recommended: (continued)  System testing (essential) ensures that the entire application, of which the modified program was a part, still works.  Regression testing (recommended) extrapolates the impact of the changes on program and application throughput and response time from the before-and-after results using the test data and current performance.  Version control is a process whereby a librarian (usually software-based) keeps track of changes made to programs.  This allows recovery of prior versions of the programs in the event that new versions cause unexpected problems.

16. 16 Systems Support Systems Maintenance - Correcting Errors  Update Documentation  The high cost of system maintenance is due, in large part, to failure to update application and program documentation.  If application documentation has changed in the slightest, it should be modified in the repository and program library.  Application documentation is usually the responsibility of the systems analyst who supports that application.  Program documentation is usually the responsibility of the programmer who made the program changes.  Recording application and program changes in the repository and program library will help future programmers and analysts reduce application understanding time during future maintenance.

17. 17 Systems Support System Recovery - Overcoming the “Crash”  Introduction  A system failure is inevitable.  It generally results in an aborted or ``hung'' program (also called an ``ABEND'' or ``crash'') and possible loss of data.  The systems analyst often fixes the system or acts as intermediary between the users and those who can fix the system.  System recover activities can be summarized as follows: 1 In many cases the analyst can sit at the user's terminal and recover the system. 2 In some cases the analyst must contact systems operations personnel to correct the problem.

18. 18 Systems Support System Recovery - Overcoming the “Crash”  Introduction  System recover activities can be summarized as follows: (continued) 3 In some cases the analyst may have to call data administration to recover lost or corrupted data files or databases. 4 In some cases the analyst may have to call network administration to fix a local, wide, or internetworking problem. 5 In some cases the analyst may have to call technicians or vendor service representatives to fix a hardware problem. 6 In some cases the analyst will discover a bug caused the crash. The analyst attempts to quickly isolate the bug and trap it (automatically or by coaching users to manually avoid it) so that it can't cause another crash.

19. 19 Systems Support End-User Assistance  Introduction  No matter how well users have been trained or how well documentation has been written, users will require additional assistance.  The systems analyst is generally on call to assist users with the day-to-day use of specific applications.  The most typical activities include:  Routinely observing the use of the system.  Conducting user-satisfaction surveys and meetings.  Changing business procedures for clarification (written and in the repository).  Providing additional training.  Logging enhancement ideas and requests in the repository.

20. 20 Systems Support Systems Enhancement and Reengineering  Introduction  Adapting an existing system to new requirements is an expectation for all newly implemented systems.  Adaptive maintenance forces an analyst to analyze the new requirement and return to the appropriate phases of systems analysis, design, and implementation.  Most adaptive maintenance is in response to new business problems, new information requirements, or new ideas for enhancement.  It is reactionary in nature -- fix it when it breaks or when users make a request. This is called system enhancement. The objective of system enhancement is to modify or expand the application system in response to constantly changing requirements.

21. 21 Systems Support Systems Enhancement and Reengineering  Introduction  Another type of reactionary maintenance deals with changing technology.  More frequently information system staffs have chose to analyze their program libraries to determine which applications and programs are costing the most to maintain or which ones are the most difficult to maintain.  These systems might be adapted to reduce the costs of maintenance. This is classified as reengineering.  The objectives of reengineering are: To either adapt the system to a major change in technology Fix the system before it breaks Make the system easier to fix when it breaks or needs to be adapted

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23. 23 Systems Support Systems Enhancement and Reengineering  Analyze Enhancement Request  The purpose of this activity is to determine the appropriate course of action to either a new business problem or idea for enhancement, technical limitation or problem, or enhancement idea (from other system support activities).  Based on analysis of current system models, that action may include:  Define new business requirements and return to systems analysis.  Define new technical requirements and return to systems design.  Define new program requirements and proceed to the next task.

24. 24 Systems Support Systems Enhancement and Reengineering  Write Simple, New Programs  Many enhancements can be accomplished quickly by writing simple, new programs.  Simple programs are those that use existing data, do not update existing data, and do not input new data (for purposes of storing that data). These programs generate new reports and answer new inquiries.  Most such programs can be easily written by end-users with a minimal knowledge of a fourth-generation languages or a PC- to-host database retrieval language, but also becoming available in most PC database packages.  Programmers and analysts are also capable of writing such programs, but some shops question whether this is a valuable use of their time.

25. 25 Systems Support Systems Enhancement and Reengineering  Restructure Files or Databases  Many of today's data stores are implemented with traditional file structures or early database structures.  Today's database technology of choice is SQL-based relational databases with object-oriented database technology gaining more and more popularity.  Migrating data structures from one data storage technology to another is a major endeavor which risks corrupting essential business data and programs.  The key player in database restructuring is the database analyst (or database administrator).  The systems analyst plays a role because of the potential impact on existing applications.

26. 26 Systems Support Systems Enhancement and Reengineering  Analyze Program Library and Maintenance Costs  Many businesses are questioning the return on investment in corrective and adaptive maintenance.  If complex and high-cost software can be identified, it might be reengineered to reduce complexity and maintenance costs.  The first activity required to achieve this goal is to analyze program library and maintenance costs.  This activity almost always requires software capable of performing the analysis.

27. 27 Systems Support Systems Enhancement and Reengineering  Analyze Program Library and Maintenance Costs  Software metrics are mathematically proven measurements of software quality and productivity.  Examples of software metrics applicable to maintenance include: Control flow knots The number of times logic paths cross one another. Ideally, a program should have zero control flow knots. (We have seen knot counts in the thousands on some older, poorly structured programs.) Cycle complexity The number of unique paths through a program. Ideally, the fewer, the better.  Software metrics, in combination with cost accounting (on maintenance efforts) can help identify those programs that would benefit from restructuring.

28. 28 Systems Support Systems Enhancement and Reengineering  Reengineer and Test Programs  There are three types of reengineering that can be performed on that program: code reorganization, code conversion, and code slicing.  Code reorganization restructures the modular organization and/or logic of the program.  Code conversion translates the code from one language to another.  Code slicing cuts out a piece of a program to create a separate program or subprogram.

29. 29 Systems Support The Year 2000 and Systems Support  Introduction  The the year 2000 the potential of triggering widespread computer application disasters across many corporations.  In the early 1960’s and 1970’s storage space was precious and Millions of applications were built with efforts to utilize as little storage space as possible.  In order to save two bytes of storage space, dates for this century were stored without the first two digits “19”.  Many applications use these dates in arithmetic operations. Numbers used to store a January 1, 2000 date is a smaller number (meaning that it occurred earlier in time), than the number storing a January 1, 1996 date, implying that January 1, 2000 occurs prior to the January 1, 1996 date. If the dates were stored with a four digit year the comparison would have been accurate.

30. 30 Systems Support Summary  Introduction  What is Systems Support?  Systems Maintenance - Correcting Errors  System Recovery - Overcoming the “Crash”  End-User Assistance  Systems Enhancement and Reengineering  The Year 2000 and Systems Support