Mini Project: Customer Maintenance Add/Change/Delete

What We Are Building

CUSTMNT, a maintenance program letting a user add a new customer, change an existing one, or delete one, extending the read-only Customer Inquiry Program mini project into a program that actually changes data.

Business Scenario

The Customer Inquiry Program mini project let a representative look up a customer's balance. This project builds the natural next piece: a screen letting authorized staff actually set up a new customer, correct a customer's name, or remove one that has closed their account.

Concepts Used

• WRITE, UPDATE, and DELETE, from the Writing Records with WRITE, Updating Records with UPDATE, and Deleting Records with DELETE lessons.
• CHAIN and %FOUND, reused from the Customer Inquiry Program mini project.
• Function keys selecting a mode, from the Function Keys and Response Indicators in Display Files lesson.

Files and Programs Involved

• CUSTMAST, read, written, changed, and deleted by this program.
• CUSTMNTD, a new display file with one record format, MNTFMT, containing an input field for customer number, and input-capable fields for name and balance, plus F6 (add), F5 (update), and F4 (delete) function keys.
• CUSTMNT, the RPGLE program tying CUSTMNTD and CUSTMAST together.

Step-by-Step Build Outline

1. Design CUSTMNTD's MNTFMT record format with input-capable customer number, name, and balance fields, and F6/F5/F4 function key indicators.
2. Declare both files with dcl-f in CUSTMNT.
3. Loop calling exfmt MNTFMT.
4. On F6, call WRITE using whatever the user typed into the name and balance fields.
5. On F5, CHAIN first, check %FOUND, then UPDATE if found.
6. On F4, CHAIN first, check %FOUND, then DELETE if found.

Example Code

dcl-f CUSTMNTD workstn;
dcl-f CUSTMAST disk keyed;

dcl-s exitRequested ind;

dow not exitRequested;
  exfmt MNTFMT;

  if *in03;
    exitRequested = *on;
  elseif *in06;
    write CUSTMAST;
  elseif *in05;
    chain CUSTNBR CUSTMAST;
    if %found(CUSTMAST);
      update CUSTMAST;
    endif;
  elseif *in04;
    chain CUSTNBR CUSTMAST;
    if %found(CUSTMAST);
      delete CUSTMAST;
    endif;
  endif;
enddo;

*inlr = *on;

Here, *in06, *in05, and *in04 are the function key indicators tied to F6, F5, and F4 in CUSTMNTD's DDS, each selecting a different action on the same screen. Notice update and delete both CHAIN first and check %FOUND, exactly the requirement covered in the Updating Records with UPDATE and Deleting Records with DELETE lessons; add does not, since a new customer has no existing record to retrieve first.

How to Test It

Test each mode separately: add a brand new customer number and confirm it can then be found with the Customer Inquiry Program mini project; change an existing customer's name and confirm the new name persists; delete a customer and confirm a subsequent inquiry correctly reports "not found."

Common Mistakes

• Attempting UPDATE or DELETE without a preceding CHAIN, which results in a runtime error, exactly the mistake covered in the Common RPGLE File I/O Mistakes and Best Practices lesson.
• Attempting WRITE with a customer number that already exists, resulting in a duplicate key error, covered in the Writing Records with WRITE lesson.
• Checking the wrong function key indicator for a given mode, causing add, change, and delete to become confused with each other.

Debugging Checklist

If a change or delete silently does nothing, follow the Basic Troubleshooting Flow for IBM i Developers lesson: check the job log first for a runtime error, then, if none appears, use STRDBG with a breakpoint right after the CHAIN and EVAL on %found(CUSTMAST) to confirm whether the customer number entered actually matched a record.

Possible Extensions

A natural extension is adding a confirmation step before delete, displaying the customer's current name and balance and requiring a second function key press to actually confirm the deletion, before calling DELETE.

Quick Recap

• CUSTMNT combines WRITE, UPDATE, and DELETE behind three different function keys on one screen.
• Update and delete both require a preceding CHAIN and %FOUND check; add does not.
• Testing should cover all three modes independently, confirming each one's effect with a follow-up inquiry.

Try Asking the AI Tutor

Use the AI Tutor to practice extending or troubleshooting this project. For example, try asking:

• "How would I add a confirmation screen before actually deleting a customer in CUSTMNT?"
• "What runtime error would I see if I pressed F5 to update a customer number that doesn't exist?"