Data descriptor FM header formats

The following tables show the formats of the input and output data descriptor FM headers.

Table 1. Input data descriptor FM header format
Byte Bits Name Contents
0 0-7 FMHL Length
1 0 FMHC  
1-7 FMHT B'0000100'
2 0-7 FMH4FXCT Fixed-length parm (X'03')
3 0-7 FMH4DTYP  
FMH4UNDF X'00' Reserved
FMH4FIX X'40' Field formatted record (FFR) - Fixed
FMH4FXSP X'41' FFR - All fields terminated by Separator (Note 1)
FMH4MXSP X'42' FFR - Fields terminated by Separator or Length defined by map X'43' - X'FF' Reserved (Note 1)
4   FMH4SEP Separator character (Note 2)
5 0-7 FMH4PCTL Presentation control byte (Note 3)
6-m   FMH4DSN Data structure name (Note 4)
m+1-n   FMH4BDT Block data type (Note 3)
n+1-p   FMH4VERS Version ID (Note 5)
Notes:
  1. From DIV or DPAGE statement.
  2. Not required, because it is received on MFS format description.
  3. Ignored by IMS if sent.
  4. DPAGE name if DPAGE selection is to be performed on the data structure name. FMT name if OPTIONS=MSG. Required field.
  5. Version ID to be used by MFS to verify that the correct definition is used to map the data. This field should be present only once for each input message if multiple transmission chains are used to create the input message. If present once for each message, it should be sent in the first transmission chain of the message. If the version ID is not sent or it is X'0000', MFS descriptor verification is not performed.
Table 2. Output data descriptor FM header format
Byte Bits Name Contents
0 0-7 FMHL Length
1 0 FMHC  
1-7 FMHT B'0000100'
2 0-7 FMH4FXCT Fixed-length parm (X'03')
3 0-7 FMH4DTYP  
FMH4UNDF X'00' Reserved
FMH4FIX

X'40' Field formatted record
(FFR) - Fixed
FMH4FXSP

X'41' FFR - All fields terminated by
separator
FMH4MXSP

X'42' FFR - Fields terminated by
separator or length defined by map
X'43' - X'FF' Reserved
4   FMH4SEP Separator character
5 0-7 FMH4PCTL Presentation control byte (Note 1)
6-m   FMH4DSN Data structure name (Note 2)
m+1-n   FMH4BDT Block data type (Note 3)
n+1-p   FMH4VERS Version ID (Note 4)
Notes:
  1. Set to 0 on output.
  2. FMH4DSN is:
    • The FMT name if OPTIONS=MSG
    • The DPAGE name if OPTIONS=DPAGE
    • The PPAGE name if OPTIONS=PPAGE
  3. Omitted if version ID not present. Set to 0 if version ID present.
  4. Version ID specified in FMT definition or calculated by MFS if the default is used. This field is present only in the first or only data descriptor FM header for the message.