Can't RPG Update a NULL Field?

["Michael Ryan" <michaelrtr@xxxxxxxxx>]

Riddle me this...I was trying to update a record using the RPG UPDATE
opcode. I first tried the %Fields parm (which I usually use), and the
fields weren't being updated. So I took off the %Fields - no change. I
had specified H AlwNull(*UsrCtl), which I thought would allow me to do
as I pleased with a null field. It wasn't until is set the fields that
I was trying to update to their default values (zeros, blanks) that I
was able to programmatically update the fields that contained a null.
Is this WAD or am I missing something? Thanks...