Rules for modifying DD statements in concatenated data sets

To override the first DD statement in a concatenation, code only one overriding DD statement.
To override any following DD statements in the concatenation, code an overriding DD statement for each concatenated DD statement.
The overriding DD statements must be in the same order as the concatenated DD statements.
Code a ddname on only the first overriding DD statement. Leave the ddname field blank on the following statements.
To leave a concatenated statement unchanged, code its corresponding overriding DD statement with a blank operand (or parameter) field.