Essentials of Subfile Programming and Advanced Topics in Rpg - Softcover

Levinson, Phil

Softcover

ISBN 10: 1882419642 ISBN 13: 9781882419647

Publisher: 29th Street Pr, 1998

Synopsis

Today programs and systems are increasingly screen-based and interactive. Subfiles are the AS/400 tool that lets you display lists of data on the screen for user interaction. Your knowledge of subfiles will increase your marketability and prepare you to move to the next level with confidence. Essentials of Subfile Programming and Advanced Topics in RPG teaches you to design and program subfiles, offering step-by-step instructions and real-world programming exercises that build from chapter to chapter. You ll learn to design and create subfile records; load, clear, and display subfiles; develop display-file code and RPG code for interactive file maintenance; create pop-up windows for user interaction; and support users with advanced prompting features and Help screens. The book will further help you link RPG programs and database files, including using the record format level identifier and the OVRDBF (Override with Database File) and OPNQRYF (Open Query File) comm! ands; mine the rich store of data in the file-information and program-status data structures; handle errors, including using the *PSSR subroutine, the INFSR keyword and LO indicators, error messages, and error logs; improve data integrity by using journaling and commitment control; and manage program-to-program communications, especially via the power of AS/400 data queues. Three useful appendices cover issues of programming standards and style, testing and debugging programs, and using Screen Design Aid (SDA).

About this title

About the Author

Philip J. Levinson brings his 15 years of experience as an AS/400 programmer/analyst, consultant, and programming teacher at Jefferson College to presenting the essentials of AS/400 subfile programming. He holds a bachelor s degree in Mechanical Engineering from the University of Hartford and a master s degree in Management from Vanderbilt University. A member of the IBM-sponsored committee that developed the certification test for AS/400 programming, Phil lives in Olivette, Missouri, with his wife and twin sons.

Excerpt. © Reprinted by permission. All rights reserved.

Chapter 1 Introduction to Subfiles Chapter Overview Chapter 1 introduces you to the basic concept of a subfile, including the purpose, design, and creation of a subfile record; the purpose, design, and creation of a subfile control record; the purpose, design, and creation of a footer record; and the RPG code to clear a subfile, load a subfile, display a subfile, and manage the no records case. What Is a subfile? A subfile is a special type of AS/400 display-file record. It is designed to hold a column-based list of data and to display that list in a column format. A subfile is a data file, with data file attributes, such as a record name and record structure, fields with field structures and other field attributes, records that contain data, much like records in a physical file. (You can add, update, and use these records for input to an RPG program in ways that are similar to the same processes on a physical file.) A subfile differs from other physical files in the following ways: It is temporary, existing only until the RPG program that creates and owns it ends; with a subfile, each field s description also identifies its screen location and its display attributes, much like the description of a field in a simple interactive screen. Subfile is an appropriate term in that we often load a subset of the records from a physical file into it. Subfiles real use is in user screens that show multiple records at one time (a list or spreadsheet-like layout of data).

Although AS/400 screens are actually built with a different technology, AS/400 Work with screens provide examples of the look and feel of subfile-based screens. For example, the WRKOBJPDM (Work with Objects Using PDM) screen shown in figure F.1 presents several elements: the header area at the top of the screen contains general information, options, column headings and some input/output fields that let the user control the displayed data, such as which library is displayed and where in the library the listing is positioned; an area in the center of the screen lists a set of objects in this case, eight at a time; just above the list of objects, the user is offered a selection of options via which the user can act upon one or more of the listed objects; function keys, defined on lines 22 and 23, provide control of global functions; the Page down key displays the next eight objects; and the Page up key displays the previous eight objects. MORE

HELP2: Using Help Records Exercises

HELP3: Using Help Panel Group The Panel Group Exercises Review Chapter 7 Creating Windows-Based Subfiles Chapter Overview Subfiles in Windows Exercises Selection in a Windows Subfile Using the Prompt Option Exercises Selection in a Windows Subfile Using Point and Shoot Exercises Using a Windows Definition Record Exercises Review Creating and Using a Window Definition Record Exercises Review Subfile Bookstore Order Project 2 Project Overview The Bookstore Order System (Continued) Section II Advanced Topics in RPG Chapter 8 The RPG Program and The Data File Chapter Overview Programming Perspectives Connecting RPG Programs and Data Files Exercise Review Record Format Level Identifier Exercise Review Access Paths Alternative Access: OVRDBF (Override with Database File) Exercise Review The OPNQRYF (Open Query File) Command Exercise Review File and Record Locks Exercises Discussion Questions File Security Exercise Review Chapter 9 File-Information and Program Status Data Structures Chapter Overview What is the File-Information Data Structure? Applying a Data Structure to the File-Information Buffer Exercise Review More on the File-Information Data Structure Exercises Review What Is the Program-Status Data Structure? Operational Data in the Program-Status Data Structure Exercise Review Error-Related Data in the Program-Status Data Structure Review Chapter 10 Error Handling Chapter Overview General Error-Handling Concepts Program Errors Using the *PSSR Subroutine to Capture Program Errors Avoidable Program Errors (Sidebar) Exercises Review File Errors Using the INFSR Keyword Using the Input/Output Operation Error Indicator Exercises Reusing the File-Information Data Structure Exercise Review Sending an Error Message Exercise Review Logging Errors to a Data File Exercise Review Using *PSSR to Avoid the Endless-Error Condition Exercise Review Chapter 11 Journaling and Commitment Chapter Overview Introduction to Journaling and Commitment Control Exercise Journaling Exercises Closing Words on Journaling Exercises

Commitment Control Commitment Control Boundary Commitment Control: Rules and Restrictions Commitment Control: CL Commands Commitment Control and RPG F-Specs for Commitment Control Exercises Placing Commit and Rollback Exercise Chapter 12 Program-to-Program Communication and Data Queues Chapter Overview Program-to-Program Communication Program-to-Program Communication Techniques Using Data Queues Exercises Review Appendix A A Matter of Style Standards and Style Program Headings Subroutines Subroutine Sequence Subroutine Headings Modifications Appendix B Testing and Debugging Programs Testing and Debugging: Part of the Job! Fast Code vs. Good Code: The Importance of Testing Syntax, Loigic, and Runtime Errors Errors Resolving Errors: The Right Suspect Using Temporary Print Output Lines Using the DSPLY (Display) Operation Using the DUMP Operation Using the Interactive Source Debugger (ISDB) Debugging Source Bode Using Function Keys Exercises

Appendix C Using Screen Design Aid (SDA) What is SDA? Creating a Simple Display File-Level Comments File-Level Keywords Adding a Record Exercise Testing Screen Designs Adding a Window Exercise Creating a Subfile Record and a Subfile Control Record Using SDA Exercise Exiting, Compiling, and Saving the Design Index

Edition details

• Publisher: 29th Street Pr
• Publication date: 1998
• ISBN 10: 1882419642
• ISBN 13: 9781882419647
• Binding: Paperback
• Language: English
• Number of pages: 481