Hi Rob,
OBJID is a transient object id. It could refer to any SF object such as volume, DG, plex etc.
INTF refers to the operation at a high level such as volume or DG operation.
MJ is major code and Mn is minor code for that operation.
The statement means that unique operation determined by INTF,MJ,MN is going to be performed on the object OBJ.
Regards,
Frank.