The Free On-line Dictionary of Computing (30 December 2018):

Common Command Set

    (CCS) Additional requirements and features
   for direct-access SCSI devices.

   In 1985 when the first SCSI standard was being finalised as
   an American National Standard, the X3T9.2 Task Group was
   approached by some manufacturers who wanted changes.  Rather
   than delay the SCSI standard, X3T9.2 formed an ad hoc group to
   define CCS.

   [Spec?  Status?  "direct-access"?]

   (1997-03-23)