FLD segment type format

The IMS catalog FLD segment type contains metadata about a field in an IMS database.

Each instance of the FLD segment describes a field for one segment in a database. This information is collected during system generation from the FIELD statement of the DBDGEN utility.
Segment name
FLD
Parent name
SEGM
Sequence field
FLDSEQ
Segment length
904 bytes
Table 1. FLD segment type format
Offset (bytes) Length (bytes) Data type Field name Description Unique key field
1 2 X LEN Length of this segment  
3 2 X CTL Control field  
5 2 X FLDSEQ Sequence field, type = U X
  5 2 X SEQNUM Sequence number  
9 8 C IMSNAME The 8-character IMS name of this field  
17 3 C NAMESEQ Indicates if this field is a sequence field  
20 1 C SEQUM Indicates whether this field is a unique sequence field (U) or a non-unique sequence field (M)  
21 2 X BYTES The length of this field in bytes  
23 2 X START The starting offset of this field from the beginning of the segment, in bytes. If this field contains data, the STARTAFT field is not used.  
25 1 C TYPE Indicates what type of binary data IMS uses to pad empty space in this field:
X
Left-padded, X'00'
P
Left-padded, X'00'
C
Right-padded, X'40'
F
Binary fullword data. Used only for MSDBs.
H
Binary halfword data. Used only for MSDBs.
  
26 15 C FILLER01 Reserved  
41 9 C DATATYPE The external data type of the field  
50 3 C FILLER02 Reserved  
53 2 X PRECISN The precision of a field with a decimal data type  
55 2 X SCALE The scale of a field with a decimal data type  
57 4 X MINOCCURS

The minimum number of elements in a DATATYPE=ARRAY field.

MINOCCURS is defined as MINOCCUR in the catalog DBD DFSCD000 definition.

  
61 4 X MAXOCCURS

The maximum number of elements in a DATATYPE=ARRAY field.

MAXOCCURS is defined as MAXOCCUR in the catalog DBD DFSCD000 definition.

  
65 4 X MAXBYTES The maximum number of bytes in a DATATYPE=ARRAY field or in a DATATYPE=STRUCT field that contains an array  
69 4 X RELSTART The relative starting offset in bytes from the end of a dynamic array or struct if an array or struct occurs in the parent segment before this field  
73 128 C NAME The external alias name of this field  
201 128 C PARENT The external alias name of another field that this field is nested under  
329 128 C REDEFINE The external alias name of another field that this field can be redefined as. This field and the field indicated with the REDEFINE field can be processed with a REDEFINES statement in a COBOL application.  
457 128 C DEPENDON This field contains blanks  
585 128 C CASENAME This field contains blanks  
713 128 C STARTAFT The external alias name of the field that directly precedes this field in the segment. If this field contains data, the START field does not.  
841 64 C FILLER03 Reserved