DSN - File control dataset name

    MACRO NAME = DFHDSND
     DESCRIPTIVE NAME = CICS/ESA File control DATA-SET NAME BLOCK
                               and BASE CLUSTER block.
          Licensed Materials - Property of IBM
           Restricted Materials of IBM 
          5655-Y04
          (C) Copyright IBM Corp. 1983, 2016 
    FUNCTION =
          Create or map an instance of the DATASET NAME block.
          This block is dependent from the File Control Table,
          and contains a dataset name (up to 44 characters long)
          or equivalently a /VSE file-ID.
          It is pointed to by any number of FCT file entries,
          for either or both the purposes:
          a) to carry a name for possible DYNAMIC ALLOCATION when the
             file is next opened. (The "optative" name.)
          b) to represent the BASE CLUSTER (in VSAM), DATA SET (BDAM),
             (or any other entity) that the file, being open,
             can update and that CICS needs to guard for backout
             integrity.
                    DATASET NAME BLOCK
     The File Control Data Set Name Block (DSNB) holds the name
     for dynamic allocation of a data set. Any number of files
     (represented by File Control Table Entries, FCTEs) may address
     a DSNB. Dynamic allocation takes place at the time a file is
     opened. At this time, if the DSNB represents a VSAM base cluster
     or a BDAM data set, further information describing the data set
     is stored in the Base Cluster Block that is part of the DSNB.
    The following fields form part of the Product Sensitive
    Programming Interface :
      FCTDNAME
      FCTDNLEN
      FCTDNVAL bit setting in byte FCTDNFL1
      FCTBCFR, FCTBCLOG, FCTBCVAL, bit settings in byte FCTBCFL1
      FCTBCFRL

                  BASE CLUSTER BLOCK

  Force doubleword alignment

  Constants for FCTBC_QSTATE. This tracks the progress of a VSAM RLS
  QUICLOSE, QUICOPY or QUIBWO quiesce request.