FMIMS builds an ACB when a user does not indicate a 'PSB or ACB' name in the Browse/Edit entry panel for a BMP environment.
The ACB is named like CAWK#nnn where nnn is in the range 000-999. When installing the product you were requested to add these names to your IMSGEN.
Along with the CAWK#nnn ACB 'DBD's are also generated in the DOTP Library. I use quotes because these are not really DBDs but by the name your might think these are DBDs.