The Technology Warrior's Guide to Modifying JDE

Go ahead. Modify the software. But don't forget the two challenges you will likely face with any modified program - retrofitting changes into future JDE releases and diagnosing system problems. Here's the safety list:

Use the Software Versions Repository.
It provides a simple method of version management ("Yo, Frank. You've got P4211 in Test and I need to add a field to the video. Are you moving your changes into Prod soon?"). It allows you to compile with overrides (subfile option 11). It reduces "severity-level" re-compiles. It adds DREAM Writer record formats to the print files. All this and more!

Use a single "Modified Source" file. Call it JDESRC.
Do we really need to break out the source code into QRPGSRC, QCLSRC, QDDSSRC, or other creative and brilliant filenames? Not really. When you use JDESRC and separate versions by library, we get fewer headaches and bill you at our "consultant-friendly shop" rate.

Don't Delete JDE code. Comment it out.
Let the analyst see what Denver was originally doing before you changed it.

Use External Program Calls or Subroutines
When at all possible, call a custom program or execute a subroutine when you are adding logic. This holds true if you add more than 10 lines of code. It makes it easier to isolate logic flaws now, as well as retrofit modifications later.

Let Original Logic do the Work.
Rather than altering bunches of JDE logic in several subroutines, change the value of video fields or retrieved data fields prior to critical JDE logic. Let the complex JDE logic think that the data really looked like that. Be sure to reset the values if appropriate.

Add Custom Processing Options.
Try to use processing options to drive custom or altered logic, rather than hard-coded decisions. When a processing option isn't appropriate to direct logic, perhaps a custom UDC table.

Use high-end VTX fields and Processing Options.
If you are adding a VTX field to a JDE video that has used the first 25 VTX fields, don't use VTX026. Use VTX040 or so. When JDE adds new VTX fields in the next release, they won't step on your mod. The same holds true with processing options (@OP).

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