When you specify the AUDIT MEDIACONTROLS VOLUMES(volser...) parameter without the SDSP qualifier, AUDIT checks control information in the common dataset descriptor (CDD, required at the start of every DFSMShsm-generated copy) in each possible DFSMShsm image of a user data set on the specified volumes. AUDIT then produces a list of errors.
When AUDIT finds a proper volume record, its content drives further checking.