The OUTREC statement with the OVERLAY parameter is used to modify or reformat specific portions of records by inserting or updating data at designated positions.

Syntax -

//SYSIN   DD  *
  OPTION COPY
  OUTREC OVERLAY=(starting_pos_of_field1_in_output_file:
		starting_pos_of_field1_in_input_file,
		,length_of_field1[,overlay_operation],…)
/*

starting_pos_of_field1_in_output_file	Specifies field1 starting position in the output file.
starting_pos_of_field1_in_input_file	Specifies field1 starting position in the input file.
length_of_field1	Specifies field1 physical length in input file.
overlay_operation	Specifies the overlay operation or data conversion operation. Optional.

Examples -

Scenario1 - Overlaying with a constant value.

//SYSIN   DD  *
  SORT FIELDS=COPY
  OUTREC OVERLAY=(30:C'NEWVAL')
/*

Inserts the constant 'NEWVAL' starting at position 30, replacing any existing data at that position.

Scenario2 - Modifying a Numeric Field with arithmetic operations.

//SYSIN   DD  *
  SORT FIELDS=COPY
  OUTREC OVERLAY=(20:11,5,ZD,ADD,+100)
/*

Adds 100 to the 5-byte zoned decimal field starting at position 11 and writes the result to position 20 in the output record.

Scenario3 - Overlaying multiple fields.

//SYSIN   DD  *
  SORT FIELDS=COPY
  OUTREC OVERLAY=(10:C'NEW',30:15,5,ZD,MUL,+2)
/*

Inserts the constant 'NEW' starting at position 10. Multiplies the 5-byte zoned decimal field starting at position 15 by 2 and writes the result to position 30.

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