During an attempt to create a mksysb resource while simultaneously putting the image on the master (using an exclude_files resource), the following error occurred:
error 0042-207 unable to allocate exclude_files resource.
Check the client to see if a master fileset is installed. If it is, remove the master, master_gui and spot fileset. Then recreate the /etc/niminfo.
A subsequent attempt to create a mksysb resource should work fine.