I wanted to add a field to a database.
That happens as an AS/400 system grows. I had added fields many times to support extensions to the systems I worked on.
My procedure was to save the original file, create a new file with the additional field, and move the old data into it using CPYF, the Copy File command.
One extra field did not mean just one task.
Even then, I felt the process was rather cumbersome and carried risks.
Then, in an old blog post dated October 1, 2024, I found myself getting excited about CHGPF.
Change Physical File.
Using DDS—the specifications that define a record’s fields and format—the command can change an existing physical file’s record format. The existing data is converted to the new format.
In that post, I wrote:
“Actually, I only found out about this recently. (Laughs.)”
And this was coming from someone who had been using the AS/400 for years.
If only I had known, I would have used it much more.
That little pang of regret was right there in the old article.
Even with a familiar tool, the ways I know how to use it are not the whole picture. Once a procedure gets the job done, it can stay with me for a long time.
Reading the article again brought back the surprise I had recorded then.
Learning new technology is enjoyable. So is finding a capability I had missed inside the AS/400 I have used for so long.
Still, all those times I recreated a file…
CHGPF, you could have introduced yourself a little earlier. (Laughs.)
A technical note for this revisit
IBM i 7.5 documentation describes CHGPF adding, removing, or changing fields from DDS and converting existing data.
Conversion matches field names. Renaming a field loses its existing data, so saving the file beforehand matters. The operation also requires that nobody else be using the file.
Convenience and preparation belong together. That is the note I want to add to this older memory.
Reference: IBM i 7.5 — Change Physical File (CHGPF) (checked November 4, 2026).