Redefining a Field in a Non-FOCUS Data Source

Redefining record fields in non-FOCUS data sources is supported. This enables you to describe a field with an alternate layout.

Within the Master File, the redefined fields must be described in a separate unique segment (SEGTYPE=U) using the POSITION=fieldname and OCCURS=1 attributes.

The redefined fields can have any user-defined name.

Syntax: How to Redefine a Field 

SEGNAME = segname, SEGTYPE = U, PARENT = parentseg,
OCCURS = 1, POSITION = fieldname,$

where:

segname

Is the name of the segment.

parentseg

Is the name of the parent segment.

fieldname

Is the name of the first field being redefined. Using the unique segment with redefined fields helps avoid problems with multipath reporting.

A one-to-one relationship forms between the parent record and the redefined segment.

Example: Redefining a VSAM Structure

The following example illustrates redefinition of the VSAM structure described in the COBOL file description, where the COBOL FD is: 

01 ALLFIELDS
  02 FLD1   PIC X(4)         -  this describes alpha/numeric data
  02 FLD2   PIC X(4)         -  this describes numeric data
  02 RFLD1  PIC 9(5)V99 COMP-3 REDEFINES FLD2
  02 FLD3   PIC X(8)         -  this describes alpha/numeric data
 
FILE = REDEF, SUFFIX = VSAM,$
 SEGNAME = ONE, SEGTYPE = S0,$
  GROUP = RKEY, ALIAS = KEY, USAGE = A4 ,ACTUAL = A4 ,$
   FIELDNAME = FLD1,,  USAGE = A4   ,ACTUAL = A4 ,$
   FIELDNAME = FLD2,,  USAGE = A4   ,ACTUAL = A4 ,$
   FIELDNAME = FLD3,,  USAGE = A8   ,ACTUAL = A8 ,$
 SEGNAME = TWO, SEGTYPE = U, POSITION = FLD2,OCCURS = 1, PARENT = ONE ,$
   FIELDNAME = RFLD1,, USAGE = P8.2 ,ACTUAL = Z4 ,$

Reference: Special Considerations for Redefining a Field

  • Redefinition is a read-only feature and is used only for presenting an alternate view of the data. It is not used for changing the format of the data.
  • For non-alphanumeric fields, you must know your data. Attempts to print numeric fields that contain alphanumeric data produce data exceptions or errors converting values. It is recommended that the first definition always be alphanumeric to avoid conversion errors.
  • More than one field can be redefined in a segment.
  • Redefines are supported only for IDMS, IMS, VSAM, DB2, and FIX data sources.
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