An FTP client can specify one or more of the Storage Management Subsystem (SMS) classes to manage characteristics that are associated with or assigned to data sets.

• Data class is an SMS construct that determines data set allocation attributes used by SMS for creation of data sets. The fields listed are available attributes that serve as a template for allocation. Each is optional and is overridden by any explicit specification of FTP allocation variables or by a model DCB (DCBDSN).

  Variable	FTP.DATA parameter
  directory blocks	DIRECTORY
  extended attributes	EATTR
  logical record length	LRECL
  primary space	PRIMARY
  record format	RECFM
  retention period	RETPD
  secondary space	SECondary

  Note: If either primary or secondary space is explicitly specified, the primary and secondary values from data class are not used.
• Management class is an SMS construct that determines Data Facility Hierarchical Storage Manager (DFHSM) action for data set retention, migration, backup, and release of allocated but unused space. Management class replaces and expands attributes that otherwise would be specified. That is, management class might override any other specification of retention period.
• Storage class is a list of storage performance and availability services requests for an SMS-managed data set that SMS attempts to honor when selecting a volume or volumes for the data set. It might conflict with an explicit specification of volume and unit. If storage class is used, volume and unit parameters should be unspecified.